Some of it still looks a little like corruption to me.
There's a huge report on this with more detail than anyone could reasonably read, somewhere way back in my comment history on Reddit. The way the problem was moved off to cross force specialised teams and then sat on is very odd, but could just be disorganisaton
They were specifically worried about race riots.
Look at the London riots years ago, that was caused by going after a gang member and escalated by gangs.
The police forces in these areas were absolutely right to worry, it wasn't just about causing offence but the real threat of organised criminal members of a community mobilising that community against the police.