In short - and that is only the Georgia case - he was trying to overturn the election result by putting pressure on a state secretary in Georgia during a phone call, which was made public, where he was telling that guy (let’s name him “Bob”): ”Hey Bob, just get me those 10,000 votes I am missing somehow…”
I may sound biased, but Trump has absolutely no respect for democratic principles if they are not delivering the results he wants to have. If this guy should get another term, he might be a real threat for American democracy.