"the mistake that would have cost 'Jurassic World' director Colin Trevorrow his job "

HR:

SPIELBERG I looked at [Safety Not Guaranteed] and thought it was really good, but I wasn't convinced until the last scene 'cause that film could have gone two ways. When this [character] who I thought was certifiably insane actually invented something that could travel through time, that crystallized the choice that it had to be Colin to do Jurassic World.

I saw an earlier version of that film in which the time machine didn't work.

MARSHALL Well [for that version], he didn't have the money to do the effect.

SPIELBERG Had that machine not worked, Colin would not have directed Jurassic World.

From the same interview:

So when you look at young directors, how do you know you're not hiring another Josh Trank [who directed the Fox bomb Fantastic Four]?

SPIELBERG Who is that?