They live up to their nickname, magpies, attracted to shiny things, no matter how cheap they actually are.
Keegan. To be fair he was a top class footballer, twice European Footballer of the year with a good career. However they had him for two seasons at the end of his career as a player when he was past it as a top flight player. He knew it himself, which is why he quit when they got promoted. As a manger he blew a 12 point lead at the top of the league. Tactically hopeless, his successes as a manager relied on him having a large cheque book at his disposal to buy the best talent he could at that level. The image of him cocking up as England manager against Romania at Euro 2000, totally lost, tapping the England badge because he had no tactical idea is long remembered by most English fans.
Rafa. The over the top adulation of the bloke was outstanding, despite him touting himself for other jobs. You'd think it was some great coup getting him, not that he'd been sacked off his last three clubs and that his best achievements in his career were nearly a decade earlier. And it's not like he's been a great success since leaving them.
Sir Bobby Robson. A very successful club manager, they almost seem to parasitically feed off what he did at other clubs and England, ignoring him they treat him towards the end of his career. I worked with a couple who for two years beforehand wanted rid of him, though denied now.
With both Rafa and Robson, they bask in the reflected glory of what they did as managers with other clubs, not what they achieved with them and rewrite history to make it look better for them, including the memes of the ghost of Bobby Robson looking down on skunk's park saying "you'll do for me".