Ok, I watched it. Def could have been an email.
Lots of speculation with not a lot of evidence. Which doesn't necessarily mean there isn't any truth to it.
Re: low numbers of DMs, the reason there are few DMs, is because WotC pushes this hardcore DM as entertainer playstyle, where Matt Mercer is held up as the gold standard. It makes DMing seem really intimidating, and I have spoken to people who don't want to DM because they don't think they could meet expectations. As opposed to when I was gaming as a kid, and just about everyone at the table was also a DM of some other campaign at some point - actually, all of the people I regularly played with were also DMs, all of us individually owned the core books, and a lot of us also had the add-ons.
If Hasbro wants more DMs, they should make DMing more accessible by promoting playstyles that don't require a BFA in theatre to participate. Get rid of the whole celebrity DM schtick. Put out modules that don't require you to heavily annotate 200-300 pages to run. IMO, the 9 pages of G1 (13 if you count the covers and the maps) are the gold standard for this.
The modules thing is particularly aggregious. They keep trying to make things easier for DMs by creating rigid railroads and lengthy if/then narratives, and end up doing the opposite by creating these massive walls of useless text. Their design requires you to keep turning to the wall of text as a reference, which makes it difficult to improvise because you never know if you are going to screw up something that appears elsewhere in the module. Shorter, less wordy modules are easier to run because it's easier to review everything in them and know that you probably aren't missing critically important information; and the older DM books expressly told you you could make up whatever you wanted to fill in the blanks.
I know I harp on the module thing a lot, but if the design of a module leaves DMs afraid to improvise because if they make an error it can break the scenario, that is not a well designed module. Even the new, less railroady, not entirely terrible scenarios that have been coming out lately suffer from this information overload.