Is it that MAGA actually cares about stopping pedophiles, or is it that the files are a tool to kneecap libs

It's both. Throughout history, people have attributed awful lies to their opponents and enemies - often about depredations against children or sexual deviancy. For example one of the oldest hatreds, antisemitism, is bound up in beliefs that the Jews would steal christian children and use their blood. The conspiracies are both motivated by and help to further motivate the hatred of the opponent. It rationalizes and justifies the hatred and the actions that are taken in response. These aren't merely people we oppose, but they are truly awful horrible monsters who do terrible things....to children, of all people. That gets people emotionally invested, it gets them willing to support whatever it takes to stop the monsters.

So this portion of MAGA genuinely, deeply hates pedophilia and attributes pedophilia to the people they oppose as part of their belief system. They think by supporting Trump they're helping to expose and punish a tremendous evil being committed by the Corrupt Elite - an evil they truly despise, and which they convince themselves is being perpetrated by the Corrupt Elite to justify the extreme measures they're willing to support and the emotional commitment they have to the fight.