I watched the DVD The Ballad of Mott the Hoople. Readily available and very good except in terms of live performances, you only get snippets.

One of the things that came across was how much Guy Stevens cared about Mott the Hoople and how deeply disappointed he was by the band’s failure while under his wing.

It was an artistic experiment that was energetic and dangerous.
"Making a record is an event. Big letters: AN EVENT. It’s not just another session. I hate people with that attitude. I could quite well die while making a record. It’s that important."

Mott the Hoople was a vehicle for Guy Steven’s ambitions and that came at a high cost: manic sessions, studio time wasted, inferior takes not corrected, and all the downsides of working with someone who frequently abused drugs and alcohol.

At the same, he inspired Mott to heights that would have been impossible without him. "Guy’s genius … finding things in people that weren’t really there," said Hunter.

Griffin says, "in the early days, Guy Stevens would tell us over and over, you are Bob Dylan, you are the Rolling Stones, you are up there with them, you are better than them. We believed him after a while, there was no alternative … he was brutal with material selection and his instinct was good."

The absence of Stevens was a key reason why post-Island Mott is so different, though for sure the band learned a lot from him which carried over.
Quotes from Campbell Devine’s biography of the band.