It’s also possible they weren’t able to see benefits given the processors that were available to them at the time.
It’s also possible that they were so far behind Waymo in the journey to FSD that they weren’t yet at a point where multiple sensors would make a significant difference.
This is my read on it as well. I listened to the same interview (it was definitely on the front page, if not at #1 for a while). I stepped away feeling like Karpathy had described a lot of good business reasons for not using other sensors, but not a lot of good technical reasons. Sensor fusion is hard, yes, but maybe not harder than perfectly re-projecting 2D pixel images into 3D vector space.
Just my interpretation, but it felt to me like a hail mary because they were fully committed to being the first mover. Waiting around for LiDAR prices to come down would have meant that Waymo would have beat them.
It’s also possible that they were so far behind Waymo in the journey to FSD that they weren’t yet at a point where multiple sensors would make a significant difference.