I can think of a few (Leigh Matthews, Kevin Sheedy, Franz Beckenbauer for example) who were super stars as players as well as coaches, but the main thrust of your point is on the money.
i didn't write that "superstars" didn't make good coaches.
i wrote that the "outrageously gifted" players didn't make it as coaches and that the best coaches seemed to be less gifted players who had to work very hard to make it as footballers including studying their game intensely and using their brains.
the three you mention fit my mold very well indeed.
yes, they were star players.
no, they weren't outrageously gifted as were, for comparison, James Hird, Michael Voss and Paul Gascoigne.
compare "your three" and "my three" as players and coaches and what do you see?
here's a few more.
Michael Voss, Nathan Buckley and James Hird.
Chris Scott, Alistair Clarkson, Bomber Thompson.
compare/contrast the player types and coaching success of those two groups.
why do rugby scrum halves, generally, not make it as coaches?
why is a rugby 5/8 succeeding as a coach very rare indeed?