Oddly enough, the three biggest cloud vendors by revenue are MS, Amazon, and _IBM_ (see links below).
IBM Cloud revenue is a head-scratcher. I've had to use them in the past, and while they have some unique features, it's hard to imagine anyone choosing them unless they had an explicit need for those features, or were forced into using IBM due to existing business relationships. I guess corporate inertia (possibly from the SoftLayer days) is a hard thing to overcome.