They missed the first round of crypto around 2013-2014 because Bitcoin was too controversial for these well established big IT companies and they were simply afraid to participate or they just missed it. So they are few years behind and now many of them are building some blockchain-related services. On the other hand setting up crypto farms and mine on them is something quite different and I guess too risky with uncertain revenue so they stick to their traditional business. Much more I would expect big banks building buying super-computers and building crypto farms (on the other hand it's probably much more simple for them just to buy crypto directly - coins are still very cheap in relations to their budgets).

Like most major companies they wait until they become obsolete before they react. The music industry did it when they ignored digital media for a decade and they almost died because of it. The print industry did it when they pushed back against online articles/directories for a decade and they almost died because if it. And now banks and major tech companies are doing it by ignoring the blockchain technologies that are being developed, and they will again likely almost die before they do anything about it.

They will join the party at some point, but only when their company is on the total brink of destruction... same shit different day basically.