This is a good article on the actual legal battles the Trump campaign are having:
https://www.politico.com/news/2020/1...lection-434360
There is a gap between the rhetoric and the stuff they actually want to test in court. Many of these accusations are specific and therefore they should be able to be proven if true.
I have no doubt there will be some disqualifying ballots. People who voted in the wrong state, people who didn't fill in the form wrong, people who cast a vote despite being a felon and so on. Many of these would be caught by the existing processes via the concept of a 'provisional ballot' but you get these problems in every election. It's completely different from the evidence of systemic and widespread fraud.
So I have no problem with Trump going to the courts on this. If it's not true it's not going to get anywhere and if it did turn out to be true then obviously that needs to be addressed. Also recounts are also perfectly fine and any campaign would request them if they lost by narrow margins.