(I am Greg.)

Starting something new is incredibly hard. The default is that your company never even forms, and it's on you to overcome the activation energy. I don't think I'd have the mental fortitude to stick that out alone.

In contrast, there's nothing more motivating than working with great people (and it's hard to do better than Ilya, Sam, and Elon). Everyone brings their own core strengths to the table, and if you've picked well your own efforts will be multiplied.