How does this fool have that kind of money? He only had one hit and one other that I’ve ever heard. 
The LP American Pie was was a big hit, and McLean wrote hit songs for other artists, including Elvis. When you own the songs, you get those royalty checks.
He had a massive hit covering Roy Orbison's "Crying." Roy loved it so much that he started covering McLean's cover!
I don't know if he's ever stopped touring - he keeps his name out there.