Should note that he was already very sidelined. Kicked upstairs, essentially.
Basically, what happened was he resigned following an internal investigation he used company funds to pay for an NDA to a mistress, which usually can be smoothed over quietly by paying back the money before it's an issue. Though it did cause the company to have to revise prior financial statements, because it turns out he'd done this before, which doesn't look good to Wall Street. Also, that happens to be illegal, though the Feds are doing their usual thorough job investigating; they do not like to lose in court and take as much time needed to make an airtight case.
However, despite resigning, he still retained a controlling interest in the company because he owned 80% of the preferred-class stock, which meant an automatic supermajority in shareholder elections for the board. This despite only actually owning about 33% of the company's total market equity. First he petitioned the board to be re-elected as chairman. They voted no. Unanimously. Including his own daughter and son-in-law. So he pulled a boardroom coup, using his voting power to install a new board that included a majority that would reinstate him. He claimed that it was to steer the company in its new media negotiations, but he really was working to sell the company.
Ultimately he put together the merger with UFC into the TKO Group, which saw UFC's parent Endeavor get 51% of the combined company while WWE shareholders got the remainder. As part of the deal, written into the articles of incorporation of the combined company, Vince was appointed executive chairman for life, or until he resigned. Apparently that was a non-negotiable condition of the sale, and he actually rejected larger offers that would have left him out. (That's actually a breach of fiduciary duty as a board member, and there is a pending class-action lawsuit against him form other stockholders.)
Regardless of that, while he was still chairman, he was told in no uncertain terms early on that he was to be hands off, leave the day to day business operations of WWE to Nick Khan, and leave the creative to Paul Levesque (aka 14-time world champion Triple H, aka Vince's son-in-law). So despite his attempts to write himself in to permanent control despite selling, he was effectively sidelined.
But then the other shoe dropped. Turns out that in his arrogance he didn't bother actually paying out that entire sum from the NDA that triggered the first investigation, giving her only a third of the money. So she filled a new lawsuit. One that, with copious amounts of evidence included, shows that Vince wasn't just a routine cheater covering up an affair.
He's a depraved psychopath who groomed, abused, degraded, raped, and trafficked the woman, and probably others. The entire lawsuit filing is online, if you want to read it. I just recommend that if you do, you be prepared to be beyond mortified. It may be better for your mental health not to read it. I'm not kidding, nor am I exaggerating. This wasn't just cheating, these were outright criminal acts. While the lawsuit is a civil case, not a criminal one, since the lawsuit filing is part of the public record, there is clearly now enough public evidence to pursue criminal matters.