You're not thinking big enough. It's not about the specific thing you're selling, it's the skillset.

Microsoft sales has a skillset of going into a company, talking to the CIO/COO/CTO/CEO and selling them infrastructure to run their business.

Google has the skills of going to the CMO or the marketing manager and selling them advertising.

Which of those skill sets translates more directly to selling cloud infrastructure?

Sure, but the point remains that this was a sales engine that was very similar. It certainly was a faster path for Microsoft to bootstrap cloud sales teams than whatever Google's long, winding path from ad sales to whatever it is they think they are doing with GCP sales.

(Though it hasn't seemed to work effectively for IBM. That may just be IBM incompetence as old school commodity-priced Mainframe mentality should be exactly the same as cloud sales. There's probably an amusing alternate world where IBM Cloud is using something like 1950s presentations only slightly modified to sell "cloud" in 2020, just because they could.)

Doesn’t matter, it’s the relationships that count. People from Microsoft eat filet mignons with the top 50 IT execs at every major company. That’s why any turd of an MS product can immediately get tens of millions of paying users.