Seems to be a common theme at the higher levels of most sports, it all boils down to mentality, look at England trying to play football, any time in the last 50 years until very recently . . . drivers crack ( Vettel) , cricketers . . . for a manager It appears to be an inability to react under pressure ( ie change a game when losing by instructing players) or to counter the opposing managers reactions. easy to say from the sofa I know. possibly just a lack of authoritive charisma if you can't gee a team up at half time for example.
The one thing they have in common is being mentally arthritic. Neither of them are premiership managers.