Has it not all got a bit market pull, rather than technology push?
Consumers saw electric motors put on hybrids, city bikes and none gnar bikes ridden by non aggressive often older riders where they worked pretty much fine and said “I want one of those on my gnarpoon sled to make the ups a bit easier!”. The companies said “You sure?” and the punters said “Yeah, gimmie gimmie gimmie!” The rush to make coin and satisfy consumer demand meant stuff that was not really fit for purpose got put together and we now have what we have.