Because IMO all that is extremely critical. I fully support the pursuit of fusion as a scientific endeavor, but given that we're probably at least 30 years away from having anything approaching commercial deployment (assuming ITER is built, works, is followed promptly by DEMO, it works, and is followed promptly by people building more reactors. That's a heck of an assumption), it's not at all a given that it'll ever make a profit. That's a lot of time to build a lot of very cheap renewables.
And there's also opportunity costs. I see a lot of hopes put on fusion and don't really understand this chasing of the perfect solution. Even best case, it's not happening in decades, and it'll take decades more to build fusion as anything more than one off multi-decade-long research projects. That's a lot of time for the world to get worse while waiting for fusion to happen, and we might as well just throw renewables at the problem now instead of waiting.
So opportunity costs would also make for an interesting thing to calculate. Given that fusion will likely not make a major difference climate/pollution-wise for half a century, what else could we build in that time, and how much and what effect would that have?