The reason they're doing this is because Microsoft doesn't control OEMs directly. They can't make Dell or whoever put in good hardware unless it's a hard-requirement to run their OS. They obviously want to start leveraging TPM 2.0, probably in order to properly compete with Chromebooks, which all require that tech already.
Chromebooks and GSuite are a meaningful threat to Microsoft - Google has a huge head start in that they've enforced much stricter restrictions from day 1 on Chromebook hardware. Microsoft is just getting aggressive about doing the same. And it's going to take at least 4 years for them to catch up, given that Windows 10 EOLs in 2015 at the earliest.
This fits far more into their business model of 0365, Sentinel, and Azure than it does with their Windows business model.
edit: Expanding on this, TPM technology is critical to Zero Trust Networking, which I'm quite sure Microsoft is going to want to push - especially since Active Directory is getting ripped out of networks practically by government order at this point. If they follow through on this, in 4 years Windows networks could be radically more secure than they are today. This fits in well with where Microsoft is taking its business (cloud, security, organization support).