John Sculley said that jobs wasn't good with running companies. Lisa failed, Apple III failed and Apple II was approaching the end of its life. The company needed cash flow to finance the Mac.
John Sculley said that his job was to turn the company around and make it generate as much cash as possible. He said this task was done successfully.
When Mac office failed, a new version of the Mac, Steve jobs went into deep depression. The Mac failed because it was slow, as microprocessors advanced so fast and made it obsolete. See also how jobs started Apple.
Steve told Sculley that he wanted to spend more money advertising the Mac but Sculley told him that the reason the Mac wasn't selling had nothing to do with advertising. Sculley told Steve he will take the matter to the board after he failed to convince him.
Sculley said that the board asked Steve to step down from the Mac division. See also why Jobs was fired.
Sculley blamed the board because he believed that there could have been a better solution. Sculley said he blamed himself for not going to Jobs and trying to figure out how to make things work.
Sculley said that he was fired later because he refused to licence the Apple Mac as he believed this can lead the company to bankruptcy. See also why Jobs used to fire people often.
Steve jobs got good experience and became one of the greatest CEOs but back then he wasn't that good at running companies.