Kaparthy had to go, anyone who takes 5 years trying to stitch a radar feed and 8 camera images together before deciding it's difficult clearly has no practical sense of timelines, or a grasp of reality.
He did not have to go.
Kaparthy left of his own accord to go back to teaching, go back to programming and away from management side of things. Musk did not want him to leave and is on the record as saying he is always welcome back. Kaparthy has also hinted he would be open to going back at some point.
Tesla had to invent new NN technologies to solve the self driving problem, they had many glass ceilings as they progressed which meant they had to change tack. Remember no one else was (or still is) doing this with Vision only, so Tesla were inventing solutions, testing and iterating continually.
The decision to drop radar, if it was as bad as they say, should have been acted upon years ago.
They dropped the radar once Vision had progressed to a level that they could compare the radar and Vision systems side by side and decided to ditch the radar.
Similar for USS I would assume, now that the occupancy networks are live, they seem to have made the decision on comparing outputs that the USS are now superfluous.
Such decisions can only be made when the new technology reaches or exceeds that of the old, it cannot be made years before.
To be honest, any sane company would have checked before shipping cars with the sensors, but thats another story.
It is likely that the decision to drop USS was made a long time ago. Kaparthy talked about this decision, so it seems it was made when he was there at Tesla and before his sabbatical, so quite some time ago.
Once made a decision would have been made on a future date to delete the sensors, they would then have to stop USS orders (in the magnitude of about a million sensors a month) and to redesign components and manufacturing processes for the USS deletion launch date.
A lot of factors would have gone in to this, and it seems the software side wasn't quite ready for the USS deletion date, so yes a miss from Tesla's side, but once a decision like this is made you cant simply revert back.
However, It seems FSD v11 is now shipping as from today, so lets see if this build includes the USS replacement code for the the new cars which don't have the sensors. If it does then the miss has only been a few weeks, with very few customers impacted.