Uh, Doctor Evil. That has already happened. Someone did make a "Star Wars D&D". They were called "Wizards of the Coast". It didn't make a bazillion dollars, though.
The way I read it, Mearls wasn't saying Lucasfilm, he was saying someone LIKE Lucasfilm. Damned if I know who though. GoT was well in the rear view mirror by then. Maybe Marvel, before they committed to their bespoke system? Maybe even Critical Role?
Regardless ... I don't entirely buy it. Too much of what Mearls says is contrary to the observed history. In the first leaks of the draft nuOGL, remember, there was that bit about how 'use of the OGL has expanded far beyond its original intent' and 'it was never intended to allow people to put out full competing rulesets' and how nuOGL was intended to fix that perceived problem. That reasoning and that line of argument was aimed squarely between Paizo's (and EN Publishing's and Green Ronin's, etc etc) eyes. Similarly, the big scary threat that WotC quoted at the time was the possbility of Facebook takling the system and putting it into the Metaverse (yes really, don't laugh!)
And the ceiling of $750k per year gross revenue beyond which crippling royalties had to be paid - that was very clearly NOT aimed at big IP companies, Amazon or Facebook or Lucasfilms, and it's ludicrous to suggest it was. The freaking
manufacturers of D&D know how much money is (or isn't...) in the RPG industry. They know the economics of the sector, and can make a solid guess at the relative scale of an organisation that's making that amount of revenue. There's absolutely no possible doubt that this figure was deliberately chosen in order to break the medium-large 3rd party publishers, to either reduce them to outsource houses, or to force them to shut up shop and go back to being individuals selling off DMsGuild.
No, I'm afraid I simply don't believe Mearls here. Maybe it's how he personally saw the move, maybe it's the line that was fed to the D&D creatives by WotC at the time, - but no, this explanation simply does not sync with the historical facts, as far as I'm concerned.