You'd be surprised how quickly people are willing to forget for the sake of the spectacle and attraction.
Greenwood will find a club. He'll find a top club in the top five leagues. The fans of that team, and indeed the leagues fans themselves will just simple forget. It seems wrong, but it's inevitable.
Floyd Mayweather was notorious for his multiple instances of severe domestic emotional and physical abuse and assault. Result? Numerous humongous money making world title defences until his retirement.
Redcafe posters didn't have a problem commenting on his fights in the boxing thread. Barely ever mentioned. Didn't want Mason back, but were happy to watch a Mayweather PPV.
My point being that outside of United fans, this will die down even in the UK eventually and barring any permanent issues with performance he'll find a club at a high level with no difficulty.