They apparently took out approx 100 document boxes of paper. They didn't read what it was, just took it all. Likely taking all the hard drives and any other storage medium. Once they get to a safe location, then they'll go looking for something they can indict him for. It's a fishing expedition. They're desperate. They know if he gets in, a lot of people are going to be fired and/ or jailed. They were already bleeding party members to the GOP. This is going to get bad. They overstepped so boldly and carelessly it won't get by those voters that put honesty and integrity above party politics. There was other, legal, less obvious and effective ways to to get the documents they wanted, but decided they needed to showboat. Trumps team were already cooperating and working with the Archives on the who the legal owner was. No need for the raid.
Or maybe something is about to go down that they needed attention drawn away from. It's gotta be big if they decided raiding a former POTUS and fishing for something to indict with, was a good idea.
However, I think this might backfire spectacularly. Which will push Trump higher and Biden much lower, if that's even possible. So I care even less now.