Most presidents receive a great deal of airtime. He was quite consistent for the most part but I'd agree more erratic after the Covid outbreak - then again many politicians around the world were like that in 2020. Finally Trump was totally at sea after the 2020 election, when should have just accepted the loss and handed over quietly.
Initially, in 2016, he was just as fit for office as many of his predecessors, and even more so than his successor IMOO. How was he a danger to the US? No new conflicts and he pushed NATO countries to contribute as per their own rules, making NATO stronger.