I myself had the same experience you did. Tuesday evening I thought it was a Trump win for sure, but saw changes on Wednesday. I of course can't say for sure what happened, but I do think that the mail in ballots accounted for some of the change. Trump mocked and railed against mail in voting, and perhaps as a result there were many more Democrats than Republicans who cast their ballot by mail. If mail votes (because they were still coming in) were counted in disproportionate number on Wednesday and succeeding days, that would be a logical explanation for a change in percentages because the mail ballots were heavily Democratic.
https://www.nytimes.com/2020/09/30/u...s-turnout.html
From the article above:
But the president has more often denounced voting by mail, issuing baseless claims that it is a way to rig the election against him and arguing that mail-in ballots are inherently suspect. During his debate on Tuesday with Joseph R. Biden Jr., the Democratic presidential nominee, Mr. Trump once again assailed mail-in balloting, citing a handful of ballots in Pennsylvania that were inappropriately discarded to argue that Democrats were using the mail to cheat.
Historically, mail-in voting has not bestowed a partisan advantage on either side. But Mr. Trump’s talk has turned the practice itself into a political issue. In polls, many more Democrats than Republicans have said they planned to vote by mail this election.