Why is a electric motor overheating dangerous? Surely any electric car is going to have a system to throttle itself if overheating is an issue, and it will need that with or without gears.

The fastest accelerating electric cars are single speed, presumably because it's not worth changing gear when you only have 2 seconds.

I can see why it might be useful in specific product categories, but when it's not helpful for price or performance or reliability, that's going to continue to be niche. The real problem electric cars need to solve right now is cost and a gearbox isn't helping with that.