. . Dan Briklin's stubborn refusal to make a CPM/80 version because he couldn't effectively copy protect it. In the business market people chose Apple IIs to run VisiCalc, and for no other reason. An Eagle running CPM/80 was a far better machine for business.
SuperCalc was already killing off the Apple II in business when Lotus came on the scene.
As for the IBM PC, yes, the Apple II did have a role. Dan Estridge asked "why is the Apple II so popular" and his answer was, "because so many companies are making money producing add-in products and software for it." The IBM PC was pretty much an updated Apple II, something Apple should have already done long before.
At the same time Steve Jobs looked at the same situation and said, "Look at all those companies making money off the Apple II. That is all rightfully Apple's money and this can never be allowed to happen again".
History is the judge.