Ironic? I think not, just follow the money, follow personal interest not ethical proclamations. Forgetting the golden rule should be a crime at this point.
Linus is handsomely paid for his work, somewhere in the low millions $ per year, the organization that pays him is the Linux Foundation which is sponsored by its members - most of all by its top tier, "platinum" members. A quick check shows Microsoft to be one of them [1].
Said members also allocate stock options to Linus, as a sign of gratitude, but those are hard to trace, so use your imagination.