They’re in the datacenter game long term. In no universe does Apple “host iCloud in other company’s clouds”. Apple is notoriously a control freak and would never place their strategic services at the whim of cloud AZs. That idea was proposed and quickly eliminated. (Believe it or not, it is possible to spend that much on Azure/GCP and still only use it for basically blobs. How do you think they moved so easily in 2018ish?)
My argument is not that specialization in informatics operations is unprofitable; rather, it's that specialization in informatics operations is indispensable for maintaining the negotiating position required to earn a profit. I'm not arguing that there isn't room in the system for the cloud operator to earn a profit; I'm arguing that after committing themselves completely and irrevocably to cloud operators, FedEx will no longer be allowed to earn a profit, or rather, just enough profit to keep their stock price from collapsing.
Now, it may be that the advantage of specializing in informatics is so powerful that this situation is unavoidable, and the only viable option for companies like FedEx is to become, in a sense, franchises of Amazon, Microsoft, Google, or Baidu. You remember when this happened to companies like Intergraph in the 01990s: they were reduced to undifferentiated Microsoft resellers. And it's not clear they really had another option. I'm not confident that the situation is currently so extreme, but maybe it is.
As other commenters have noted, you were pretty comprehensively wrong about iCloud, but that's a minor supporting point.
Apple fairly notoriously hosts iCloud in other company’s clouds, and they’re a computer hardware and software company! If you’re less sophisticated than Apple, it’s a no-brainer to go with clouds.