I think politicians just didn't want to deal with it because they didn't want to rock the boat over what was essentially football fans.

Even Thatcher felt that the Police were being evasive and dishonest but she didn't care enough to push the issue because she privately regarded football fans as scum.

Blair and Straw didn't want to push the envelope because what was in it for them.

It was less of a cover up by politicians than a concerted and long lasting shrug of the shoulders, the only politician to actually do anything was Andy Burnham.