It doesn't just involve people's political enemies. For example, the Clintons and Trump have gone to Jeffrey Epstein's "Sex Slave Island" on the "Lolita Express". When it comes to Jeff, he doesn't support either side. He sees all (or almost all) politicians as criminals. So I guess you could say, in a sense you're right.

The reason every big politician would be a paedophile (according to the hypothesis) is that politicians are either:

1. Controlled by a hidden government which, over time, encourages them to do more and more depraved acts, to use against them in case they ever decide to get out of line
2. Many politicians are psychopaths, and so they need to find a way to make sure they can trust each other. When everyone has the dirt on everyone else, they can sleep sound.

I don't know why footage doesn't get out. Perhaps it's because this sort of thing actually isn't that common, or perhaps it's because the penalty for letting this stuff get out, is death.

With regard to the police, that's an easier question to answer. There are many cases where the police in the UK had an opportunity to stop a paedophile ring, but didn't. In one famous case, they didn't want to arrest the Pakistanis involved because they didn't want to appear racist - that's the popular story. More commonly I think they're told to ignore it, threatened into ignoring it, or bribed into ignoring it. Politicians pull strings and police are powerless.