IMO, Trump will mail this campaign in and I think it'll become more obvious as he gets increasingly more weird. He's not prepared to campaign effectively against Harris, and I think it's incredibly naive to believe he's going to miraculously turn the tables during debates. It's not 2016 anymore, a lot has changed socially/culturally, and he won't have the weight of his zealous social media presence like he did the first time around.
The GOP infrastructure is hallowed out, Harris is out-fundraising at a 3:1 or 4:1 clip over Trump, and the R's really don't have the machine to do much with their money besides let Trump do what he wants with it.
I think Trump would drop out if he could figure out a way to make more money out of it. But, mailing it in, crying about media bias and a stolen election (again), is the way to keep the con going and bring more money in for himself.