Some media sales-people would be super comfortable selling enterprise stuff (because a bunch of them started at MS/Oracle/Sun etc).
The front-of-house salespeople would be fine, so you'd just need to hire the back-of-house sales-people (normally the more technical ones).
The real problem is that Marketing and IT are very different departments, and it's hard to change contacts in one area into opportunity in another (I think this applies to both Google and FB).
But mostly, to answer the titular question: it's about margins, nothing else. There's less money in cloud than in ads. So, like Google, they'll probably do something like this when investors start to worry about the ad market.
It's the opposite in enterprise tech where Google is the underdog and needs to do quite a bit of selling, and base it on the strength of the product and functionality. GCP is hiring strongly for enterprise/software sales experience but struggling with the leadership to use them effectively.
There's plenty of margins in cloud though. AWS has proven it and GCP has the potential to be bigger than their ads business, but I agree that it's not currently as lucrative today.
Paraphrasing OP: Google knew how to sell ads, not how to sell cloud...
- The Dynamics suite
- Visual Studio / TFS
- Windows Server family products
All of those were "cloud-adjacent" even in their proto-forms as on-premises–only offerings. Even if they weren't "real cloud infrastructure" they were big Capital-E Enterprise products and a lot of selling cloud is still B2B Capital-E Enterprise work at the end of the day.
(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.)
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?
Google had experience in the former. Microsoft had endless experience in the later.