Erm it's pretty simple actually. Collins is a defensive specialist who can block up the paint and defend elite big men like Howard- putting him out there isn't going to affect the win/loss comlumn because Collins' weaknesses/strengths are generally a wash.
Umm...you do realise that Collins had BY FAR the worst net off/def rating on this team last year right?
He actually had a very poor defensive rating, and he had the worst offensive rating on the team. Add those together and his net rating was at least twice as bad as any other player on the team.
Crawford is like Lebron James compared to Collins.