I don't think Elon has ever aimed to specifically be a "climate activist". His positive effects on the environment seem more of a side product from making the "crappy but sustainable, will be cool in 10-20 years at current pace" option "cool+useful and sustainable, now". Which makes sense, he would probably have gotten less done environmentally and generally if he didn't have success of the businesses as clear priority.
I think he stated that his underlying big plan was to act in fields that he thinks will have the most impact in the future, being good business while not just profit-driven, after he got the PayPal money (Can't find a source right now though) in which he has succeeded, profiting from making the world better, instead, for example, lobbying against ICE's and then providing "just-good-enough" Environmental(r) ShittyCars(tm)
He also has shifted his focus accordingly when Tesla, and at part, SpaceX, were at dire straits. For his kind of personality, I'm not sure just working more would even transfer as simply to linear benefit on that thing.