I really think that the competition among bullet companies is the real reason we see so many changes in bullets.
No different than 3 car washes in the same town all just offering a nice clean car.
But they all seem to be doing it for whatever the reason.
Back in the early fifties, it was a 139 gr 6.5 bullet introduced in this country by Norma, which caused the creation of the 6.5x300 Weatherby cartridge and lots of excitement among long range hunters at that time.
It was known to be a very good performer on deer at long ranges, even though it was illegal to use in PA, where much of that type hunting took place. And the reason was it had a metal jacket attracted to a magnet, which the law there still forbids.
Im still using 162 gr Hornady 7mm bullets i bought in the 70s, but that same bullet has seen several changes since, including a considerable drop in the BC #.
One thing hasent changed though, that being where you hit them and how much blood loss it causes.