He really is/was smart about some things - marketing and self-promotion. He started with millions and ended up with hundreds of billions, all thanks to his marketing skills, and knowing how to be in the right place at the right time.
Being good at one thing doesn’t automatically mean he’s good at other things - like running a company, or being an engineer as he likes to imagine himself.
Cursor is not really anything that I feel a need to customize. It’s a pointer that changes shape according to context, and the default implementations usually do it at least decently.