I don't work in the industry and am not an expert, but I think a part of it in recent years is that lithium ion manufacturers have been figuring out how to get

I don't work in the industry and am not an expert, but I think a part of it in recent years is that lithium ion manufacturers have been figuring out how to get by with less cobalt in nickel-manganese-cobalt batteries. If you read about 622 or 811 chemistries, those are the proportion of nickel, manganese, and cobalt. So, the older 622 batteries are 20% cobalt, and the newer 811 batteries are 10% cobalt. Manufacturers are trying to move to 5%, iirc. (This doesn't apply to lithium iron phosphate, which doesn't use cobalt at all as far as I know.)