On April 10, 1985 Apple CEO Sculley gave the Apple board of directors an ultimatum—he was prepared to resign if they didn't remove Steve Jobs from running the Macintosh division. Of course as the CEO Jobs had recruited and hoped would mentor Jobs to be a leader someday, this was seen as a betrayal. Job was not only an Apple founder, he held a large amount of Apple stock.
At the time the Macintosh had been available for over a year and January 1985 saw the Macintosh Office announcement (and Lemmings tv commercial) but Macintosh sales hadn't picked up. Jobs was frustrated by the high price of the Macintosh (by then the Macintosh 512k, or Fat Mac) and he felt the future of the company was with his division. Sadly the Apple II division was the company's breadwinner and Jobs overplayed his hand.
The board backed Sculley, leaving Jobs with no role inside Apple. Sculley went on to put Jean-Louis Gassée in charge of the Macintosh division where he oversaw the release of several Macintosh lines including the Macintosh II which finally brought to market slots and a case owners could open.
This showdown lead to Jobs eventually leaving Apple to found NeXT. He also dumped most of his Apple stock (reportedly keeping just one share) which amounted to about 11% of the company. It earned him over $100 million dollars, money he used to purchase the computer animation division of Lucasfilm which he eventually renamed Pixar, but that only set Jobs back $5 million.