Fortunately there is no need to do it with just vision. There is also no need to do it without vision. On the quest to make the first self-driving cars, most researches have decided to use the full toolset at their disposal, and there's not a strong argument why not, unless you've already sold a few million cars with a more minimal sensor suite and want to try to make those work.
As is often the case, this argument completely denies history and commercial reality.
As I understand it Tesla defined the major bones of its current hardware package back in HW2, which was late 2016. They now have a massive fleet of vehicles with a vision-only hardware package for which FSD has to eventually be functional. It is all very well to say that the cars would be better equipped with lidar/radar/sonar and deely boppers, but that won't help the existing fleet. It is also true, despite the whining on this forum, that Tesla are still making progress towards their goal with the current hardware, and with the possible exception of Waymo (who are playing a different game really), still one of the leaders in their field. They have no compelling reason to take the hit that would be involved in changing tack at this point, it goes well beyond 'want'ing to try and make it work.
So why did Tesla not do the seemingly obvious thing in 2016 and stick all the sensors on the cars then? Looking more to decisions based on fact, Tesla's net income for 2016 was
minus $675M and the most expensive vehicle they were selling was the model X at about $115,000. Their entire deployed base was 186,000 vehicles with the Model 3 yet to make it big and the company was still in an extremely delicate position. EVs were not freakishly rare but still pretty niche.
So, against that background - the hardware on a 2016 Waymo is estimated to have cost $150,000. Where would you expect Tesla to get the funding to have put that on their vehicles? Who would pay for it? They wouldn't have sold many Model 3s if it had debuted at a price point of $180k, would they? Add in to that the fact that Waymos look 'fine' as a taxi, but with all those sensor clusters they're butt ugly by the standards of private vehicles and that matters if you want people to actually buy them.
You can say 'perhaps you shouldn't
sell cars that can drive themselves before you can
build cars that drive themselves' and that's a very fair point, but that's not how Musk works, and despite the fact that he increasingly appears to be an awful human being, it's hard to imagine who else would have taken Tesla on the growth journey it's been on.
And as a final mic drop, Waymo have been driving around carefully curated areas for the 8 years since then WITH a $150,000 fridge freezer on the roof (yeah, I know it's cheaper and smaller now) and they're still running in to other cars and construction zones so it's not like the extra sensors are a magic bullet.