From a historic perspective gold and silver are considered money. Central banks hold gold and it is an ancient currency, platinum on the other hand was fairly recently discovered by new world explorers. The jewelery and automotive catalyst industry are the main consumers of platinum from what I’ve read, although investment demand has probably risen over the years. On the weak end of platinum investment I see a substitution effect coming from its sister metal palladium. Palladium is much cheaper, can also be utilized as a catalyst and when alloyed correctly will look like platinum, it would be much lighter though.
Pretty sure the only platinum/palladium mine operating presently in the lower 48 is Stillwater mine in Montana. Where gold and silver are mined many places, the concentration of platinum/palladium mining is South Africa, Russia, and North America. As far as your Russia story, it was my understanding that Norislk Nickle likely stockpiled large amounts of palladium and probably platinum over decades of mining nickle. Although it’s basically a state secret, there have been rumblings that those stockpiles have been or are being depleted. That could have been part of the big move in palladium last year.
Hope that helps a bit, in closing…. almost all the gold mined is still held while plenty of silver, platinum, and palladium end up in the landfill. The landfills that will probably be mined one day…lol.