It's possible that Trump is not guilty of collusion because he is a moron. Trump on the campaign trail mostly held rallies where he belittled people to the cheers of the crowd, attended debates where he belittled people to the cheers of the crowd, and tweeted deragotory stuff about people to the cheers of the twitterverse. He also wore a hat. That seems to be about the extent of his efforts.
There were others around him who were smarter and more devious and were trying to help him win so that they could affect policy at the highest levels of the US government. And, to their surprise, they won. And, then they had to govern, which was probably boring.
Trump returns to the rallies again and again because that's his thing, ranting to a friendly crowd and looking powerful by firing and insulting others. It's entirely possible that he is not guilty (but others around him are) because he just was not plugged into the mechanics of the campaign, because he is a moron.