It is easy to point to Trump wanting to stay out of prison as his primary reason for wanting to be President again. But there is a more subtle reason that gets missed.
Trump has lost the ability to make money. His corporations are being shuttered, he will by facing stiff monetary penalties, his brand is in the sewer and banks won't touch him. So all he has left is his CPAC's and his red cap donors that are giving him money monthly on autopay. They think their funds are going to Make American Great when they are really going for Trump's legal defenses. Trump knows if he can get back into office the foreign nationals will find ways to enrich him like they did during is 4 years. Not to mention, selling off our national policies and resources, secrets to the highest bidders.