This isn’t a court of law. That was Trumps lead the day after. Then the real shenanigans started. For days “votes” were found and thousands and thousands of illegal ballots were counted. Whether you choose to believe it is up to you.
They weren't necessarily "found." They were filled out and mailed before Election Day, and then mailed by the deadline for mail-in ballots in PA.
It took days to count them.
I have no doubt that many of them were illegal. There's no evidence to support the claim that the illegal ballots numbered in the thousands -- because the mail-in voting process makes it impossible to track them.
What happened in 2020 was that Trump was running around telling his supporters not to vote by mail. Meanwhile, Joe Biden appealed to all the losers who were perfectly content to sit at home and mail in their ballots. That's why Biden had an enormous margin in the mail-in ballots that were counted after Election Day.