How did Waymo do this? As far as I know, replacing drivers with an AI was the goal of ever-money-losing Uber and Lyft, however, Waymo managed to get to this much sooner while having less funds.
I've also not seen much drama coming out of Waymo in the past. I could be wrong but I guess this is the benefit of keeping your head down and focussing on the problem instead of growing too large.
Waymo existed for like a decade on the basis of "we have a pile of money and our founders think it's cool". They moved slow and broke nothing. They made slow, incremental progress exploring the self driving space for years with plenty of funding and no expectation of a product launch.
So when a bunch of other companies came along, years and years later, and were all "we're going to have self driving cars next year!!!", and Waymo had their "oh shit, we better actually make this into a product or why do we even exist " moment, they were already in a really good place. They weren't rushed, they probably could have pivoted to a product a year or three earlier. They'd already solved the problems everyone else was just handwaving.
If it was accidental, they sure got lucky in the amount of time they were given with relatively little pressure, and in the timing of that competitive pressure at the end.