Maybe you're onto something, maybe not, I don't know. I figured Greece won that tournament thanks to playing in a style that was very out-of-vogue at the time, to the point that many of the teams they played against simply didn't know how to face a team playing like that because they'd not done it before. They were compact, well-organised and able to nick that one goal that would win it. As to the phenomenal fitness, Stelios Giannakopoulos was fined by his club team for going down with cramp inside 90 minutes in one of the games, on the basis that if he was looking after his fitness he'd be able to go 90 minutes without cramping up.
I cheered them all the way to it as underdogs, but at the same time it put the cause of the sport back a long way from an entertainment point of view, as now you have lots of identikit national teams who have organised and structured defence and no playmakers or born goalscorers, whose style of play is all about getting the 0-0 or 1-0. This leads to very frustrating games because if they're level, they just stifle the opposition and prevent exciting football being played, and if they fall behind then more often than not they roll over and play dead because they simply don't have any weapons for getting themselves back into a match.
And as soon as teams cottoned on to what the Greeks were doing and worked out ways around it, they were swiftly returned to their usual spot in the European football pile.