I guess you can call those technicalities, but more accurately they were trying to use the court system to wage politics and the courts both liberal and conservative all looked at what was filed and said they were absurd and baseless.
I'm not going to put any links here to avoid steering too far into politics, but I'd recommend looking up the comments many judges made about those "cases" and the lawyers presenting them.
Have you read any of the court documents from those 60+ lawsuits, or did someone tell you that?
I did. So can you. As I said before: educate yourself. Or don't. It's no skin off my nose. But you do put yourself at a disadvantage when you don't know the facts.
Go and read the court documents. They're quite accessible, both online and in their use of language.
I expect that you'll find (despite judges not agreeing) some cases that you think might have merit. I also expect you'll notice that the vast majority are hogwash. With no evidence at all.
But I'm a lying liar, right? Probably a communist too? Okay, fine.
Don't believe a word I say. Go and read the court documents.
You asked how you could be sure about (the lack of) voter fraud. How can you be so sure about fully documented lawsuits you haven't even read for yourself?