@Flaming Carrot
Regarding on what you said about Lucas' Sequels wiping out the Thrawn books, there was also the fact that most of the EU fans were not big fans of Lucas prior to the Disney buyout. This whole reverence for the man after TLJ dropped was something that was very recent; it's not even ten years old. It only happened because Disney made a misstep and thought they'd be lauded for "subverting expectations" in TLJ. If they continued to shamelessly pander to the OT fans with nostalgia bait and cameos, or had the Luke and Leia power fantasy hour with both of them being fully-realized Jedi acting as the Kenobi and Yoda to Rey in the Sequels, people would've kept praising Disney and lambasting Lucas as inferior.
The "Lucas Rehabilitation" as I call it, was certainly helped on by TCW making the Prequels' plot be dumbed-down enough so that normies and little kiddies could understand it and go "so that's what Lucas was trying to do with the Prequels!" But despite that, even guys who read the books or played the games still looked at Lucas like he was an idiot for writing the Prequels, and even fans of the EU saw him as a black sheep for it. So there was no love lost when Lucas sold Disney and Disney canned the EU. He didn't resist, he didn't talk back, his "White Slavers" comment was directed at the Sequel Trilogy and he retracted it soon afterwards.
I can just imagine the sheer FURY that the EU fans would've had for Lucas if he DID hang on to Lucasfilm and create his intended Sequel Trilogy; it would step over countless books from the Thrawn Trilogy, Dark Empire, Crimson Empire, and so much more. The people who enjoyed those books will be up in arms about it, while the only stuff that stays safe would be the Old Republic stuff since Lucas wasn't interested in that part of the timeline.
At the end of the day, Lucas DID support Dave Filoni getting the power to rewrite the EU to fit his standards for the TCW show, and Lucas would've probably done the same thing to the post-ROTJ lore and get rid of things he doesn't like, such as Luke getting married with Mara Jade. No Vong, no Thrawn, no Dark Empire, no Jedi Knight games, (all three JK games take place AFTER ROTJ) and all of it would've been retconned for whatever plan Lucas had for the Sequels.
So if anything, the result would've been the same, and with Lucas being tight with the leftist crowd (remember, this guy thinks the Viet Cong were the good guys and Nixon was the bad guy in the Cold War, to the point where the Rebel Alliance was modeled on the former and Palpatine was inspired by the latter) he wouldn't be that averse to putting pro-SJW stuff in it. Plenty of authors who were politically incorrect back in the day and put in raunchy stuff in their past work *cough* Garth Ennis *cough* Alan Moore *cough* are now pro-SJW and are tight with the LGBTQ crowd.
If Lucas did the Sequels, you'd still have a lot of the old EU getting wiped, you'd still have social justice making inroads into Star Wars, complete with Lucas' blessing, and the hatred and wrath of the EU fans would be pointed at Lucas instead of Disney. We'd be talking now about how evil Lucas was for shitcanning the EU and how he bent over backwards for the Leftist SJW plague, and people would still be talking shit to him about the Prequels. Lucas is a more left-leaning Christian like say, Pope Francis, and he wouldn't be that averse to leftist causes in Star Wars, when the fucking Rebel Alliance was inspired by the Commies in Vietnam fighting against the Empire of Cold War America in the first place.
If anything, selling to Disney and letting them do the Sequels probably saved Lucas a lot of grief. That way, when they shitcanned the EU and did their Sequels, all the glory
and the blame will be on Disney's head, while Lucas can retire with his wealth and livelihood. And now that Disney's fucking up, people are praising Lucas, so it's a win-win for him. His Prequels get rehabilitated in the eyes of the public, he doesn't get the blame for the ST shitting all over the EU, and he still has all that money. To Lucas, Star Wars begins with TPM and ends with ROTJ, he couldn't give less of a shit about the EU and everything else; the most we've got is him inspiring plots in the EU like Force Unleashed and Dark Empire, and those weren't the most well-loved stories in the EU, now are they? They were at best, seen as average-to-good by some fans in those days, (I thought they were great, but that was far from the average opinion) while other fans laughed at them for being power fantasies with ridiculous premises.
TL;DR, Disney was the canary in the coal mine for Lucas' Sequel plans. The fact that they did the ST and canned the EU allowed Lucas to dodge a bullet and get some positive PR in exchange once Disney started pissing off fans.