Which is exactly why he failed here. Can't handle the big stars/signings, because he has the mentality for an underdog, middle of the pack kind of team.
I'm sure he'll do well with West Ham this season, top 10 finish probably. But as soon as the fans start demanding more and the owners give him a lot of transfer funds, he'll fail to deliver that next step.
That is also a bit of a stretch. It's not like he failed every big transfer ever. It's just that he's really good at the bargains and is more known for that.
Fellaini was actually an expensive signing of his at Everton (I misunderstood early when I said he was a bargain) and he was a big hit at Everton and could play several positions.
His other bigish signings were Andy Johnson, Miralles, Beatie. I mean it's not like "he cant handle big star/signings" at all. That's yet to be seen. Mata was one of his signings and he's lasted what 7 years now.
He's just never been a big spender in general and that's largely also due to his situation at teams.
Again, his lower level signings are insanely good:
Coleman, Cahill, Stones, Arteta, Pienaar all for around 9 million total.