I love Crowder, but lets be honest, he isn't a starting SF or SG. I think Snell at times seemed hesitant, but hes a rookie who has yet to even go over the cusp of his potential.
The main criticism with Snell isn't that he has no potential or high ceiling, but the fact he wasn't aggressive enough. He has a very high vertical jump, and athleticism that shoots up through the roof if you watch the Basketball breakdown by Coach Nick.
I suggested this trade, because even if they lose the 3pt shot from Snell, they got McBuckets to possibly replace him or as a sixth man. Plus Crowder and Butler would fit well, and maybe give Butler the incentive to stay alongside his good mate from college.