What convinced you to come back to Dominion and create a new set? Other than money, which is a totally valid reason.
It wasn't money; it's nice to have a project that you know will get published, but uh a Dominion expansion has no chance of being a dud but also no chance of being a big hit. It only sells to the portion of Dominion fans that want another expansion.
All the reasons for doing spin-offs instead still stand. But I made a spin-off and took out the Dominion part and that's Kingdom Builder. And I made another spin-off and took out the Dominion part and that's Temporum. And it seemed like, even if I manage to make some spin-offs, I'm sure not cranking them out like I once thought I might. So at some point I would be making another Dominion expansion, for the publishers and fans that I wasn't offering spin-offs to. And one day it seemed like a good project to work on next.