Many reasons have been advanced for Keegan's sudden, if not totally surprising, departure from St James' Park last week after four years and 11 months as manager and messiah who took Newcastle out of the mess. There were private matters, family considerations and the health of his wife; the board's refusal to sanction more signings, a strained relationship with his chairman Sir John Hall; even that his hair, once black and white as if to show commitment to the club, was now just white due to the pressure of it all. Actually, while all probably contain some truth, it is undoubtedly down more to a grey area.
Money and the need to accumulate more of it, as might be expected in modern matters Premiership, is at the root. Newcastle have seen what Manchester United have achieved by public flotation; it was the way to compete, physically and fiscally, they surmised. Keegan had his doubts, as he told me in probably his last one-to-one interviews a month ago.
"I think we will look back on these last five years as the most exhilarating in the club's history," he said. "With going public, a signing like Alan Shearer's may never happen again. It may be the way we match and maybe beat Manchester United but we might lose something else. You have shareholders to answer to, permission to get. At the moment we have an edge in things like that. We can take a decision and get on with achieving it."
That was proving increasingly difficult, however, with flotation imminent. In the spend, spend, spend days, Keegan could sit down with Sir John at Wynyard Hall over a drink and convince him of his need for a new player. After an episode in his first month when he was refused and threatened to resign, Keegan received the carte blanche to do things his way.
With Sir John now more occupied with other areas of his Sporting Club empire, his son Douglas becoming increasingly influential, it probably began to seem to Keegan that it was more end of empire, that the exciting, pioneering days were coming to a close. My way? More likely the chairman of the plc's way.
Getting to speak to Keegan that week said much about the changed face of Newcastle. Faxes and phone calls to press officers and secretaries yielded only obstructions. Finally, frustrated by official channels, I tried the mobile phone number Keegan had given me in the days before the perm turned, when he felt less wearied by the demands of the job. On contact, he was as honest as his naturally open character had always made him, as if forgetting for a moment that he was not supposed to be so accommodating these days. On reflection, though, there was wistfulness rather than enthusiasm in his voice.
Now, this correspondent's mind inevitably wanders back to Keegan's first match in charge, against Bristol City at St James' Park on 8 February 1992, when the Cheviot Hills were alive with the sound of music to the ears of Geordies at the return of the man once called football's Julie Andrews.
Newcastle has always been a hotbed of the game, though then it was a hotbed of nails. A rousing 3-0 win promised relegation to the old Third Division would be avoided, even if that promise was only just kept on the last day of the season. After it, all freshness and vitality, Keegan leapt into the press conference with a single bound. "This is the first letter of the first word of the title of the book," he said.
There were heady nights in the subsequent narrative. One recalls a 5- 0 win in Antwerp when all his attacking ambitions were joyously realised. "Any chance of an interview for Sunday, Kevin?" we asked. "St James', Thursday, all right?" he replied.
Such days and nights disappeared in the desperate disappointment of what followed, when Newcastle were relentlessly, almost cruelly, reeled in by Manchester United in last season's title race. The outburst in reaction to canny Alex Ferguson's psychology, the refusal this season sometimes to speak to the press were out of character. Perhaps Keegan himself realised it and was uncomfortable with the tetchiness gnawing into him.
"You watch. As soon as he gets any criticism, he'll be off," a former Liverpool playing colleague of Keegan's told me two years ago before expectation had overtaken the vibrancy. In many ways, the surprise is that he stayed so long. Criticism clearly did sting, but its spirit may have been overlooked.
You wanted him, as a neutral, to shore up that defence, to rein in only a tad when appropriate, so that last-minute goals at Liverpool would not be conceded and the breathtaking fluency be rewarded with silverware. Sadly, that will not be the legacy, though the rebuilt stadium was built with money his inspirational leadership persuaded fans to part with. Beyond that, we will not forget the charisma and panache - intangibles that do not show up on balance sheets.
For Sir John and his board, though, that is the bottom line. Though it is tempting to impart some blame on them - their reserved statements of appreciation hardly impress, either - Keegan had a deficit of pounds 40m on transfers, roughly the club's debt, which makes the imminent flotation that precipitated Keegan's resignation the only real option. Not to have declared that the manager might go at the end of the season, as he wanted to last May, would apparently have been to break Stock Exchange rules about information relevant to prospective investors.
It all illustrates how the game is more than ever hostage to finance. Amid the wealth of coverage that accompanied Keegan's departure, as evidence of the phenomenon that football has become and the phenomenon he created at a club whose impact on the culture and well-being of a region is gargantuan, it was put to a financial analyst that his sort would now be the leading players in the game. "We're already in the boxes," he said. Some of us prefer the more truly knowledgeable company in the cheap seats.
What now, who now? A worry here is that in the future a new manager will have to be acceptable to the City. It may not necessarily be the right man for the job in footballing terms, but instead a character, a personality, who can lift share prices as priority over performances.
The gallery of potential replacements lined up in the aftermath was almost comical in places, with unqualified hats being thrown into the ring. To expose Peter Beardsley to the job would be unfair to him until he has better absorbed the trade of coaching and management.
Had Keegan been better grounded, he too might have endured the position longer, even if he was then the right man at the right time. The English have for far too long valued the big-name, ex-player Mr Motivator, preferably chatty and flamboyantly dressed, above a man of more understated, but enlightened, tactical and technical virtues. More power to Arsene Wenger.
In this correspondent's opinion, the right man is a short hop across the North Sea, in Amsterdam. At the end of this season, Louis Van Gaal will leave Ajax and is awaiting offers. He has already turned down Milan, preferring a fresh canvas to working again with so many of his former players. "Newcastle is something that could interest him," a close friend of his told me. Van Gaal returns from an Alpine skiing holiday today.
The Dutchman is a man who would want total control of the club - but only on playing matters. Newcastle, like all Premiership clubs, clearly need such a figure, who can oversee the development of youth policy and proposed football academy and who also knows his erudite way around the European game. After the messiah, the call should be for a prophet.