Same thing really with Peter Adkison, though in somewhat more amicable circumstances.
Basically, when forming a corporation, you can basically assign the ownership however you please. You can, for example, decide that one person owns 50% and the other 50% are owned by the corp itself, so it can then pay others for things with shares. When forming Wizards of the Coast, both Adkison and his legal advisor was, let's say, not enthused with the finer nuances of capitalism, so basically all the shares were owned by Wizards itself and not by Adkison. Adkison would then take shares as part of his pay for being CEO and stuff, so it's not like he didn't have any ownership stake at all, but Wizards paid a lot of their early workers and contractors partially in shares so Adkison never had a majority in the company.
So, when Wizard had gotten the license from Nintendo to make a Pokémon card game, that was making them a lot of money. Probably not as much as they're making now, but it was a big boost to the company. This in theory made the company worth a lot of money, but since it was privately held it was hard for shareholders to turn that potential money into actual money. So a bunch of them told Adkison to either find someone to sell the company to, or to take it public so they could sell their shares. And since Adkison didn't have majority control of the company, he found himself a Hasbro to sell it to. Hasbro kept Adkison on as VP, but when Hasbro sold off the digital rights to all their games (including Wizards games) over his objections he quit.
It would be interesting to see the alternate reality where Adkison was competently advised when forming the company and kept control and didn't have to sell out.
