I have a similar issue, I can find motivation to start something but then it spirals into other things.

For $100 million I would probably just learn to put on the scuba gear but for instance my mind would go to "I should make my own scuba gear". So for a personal project I start on something and decide I need something else, so then I want to make a tool to help me make that thing and so on. I think it's probably related to a shorter attention span so I'm working on that.