Trump still claims he won in 2020 - wouldn't that invalidate his election in 2024?

Except, according to Trump, he won the electoral college. In all the stolen states, the real electors met and cast their real votes for Trump. They then sent their real votes to be counted by Mike Pence. He claims he has >270 real votes on his side, and therefore won the Electoral College.

Was that remark addressed to BigT ?

You may have misunderstood. BigT, I believe, was just quoting Trump’s claim, but clearly does not believe it to be true.

It doesn’t matter what Trump thinks. The actual electoral college chose Biden and that’s that.