The older I get, and the more useless charlatans who come and go, the more I think that the vast majority of managers have very little idea at all what they are doing, and are getting away with it, frankly, either because their name makes them an employable brand, or because they are occasionally blessed with good squads who do the hard work for them, or because they always work with top-notch support teams, or whatever. I reckon this is true at all levels of the game, too, all the way to the top. In that respect, football is just a mirror of senior management generally, in corporate/institutional life today.
The minority of managers, however, who really DO know what they are doing, can make an enormous, positive impact, very quickly. Ironically, on the day he's been sacked, the one who really brought this home to me was Danny Wilson during his time at the Lane. Whatever his limitations, DW, bless him, transformed our style of play from unwatchable shite to something more than alright, more or less overnight. (You could make a song out of that ?) . The manager who has recently reinforced all the above for me, is Sir Christopher Wilder.
On a bad day, good luck to you Danny Wilson ...