That's completely nonsensical. Microsoft didn't act anti-competitively to become big, they did it AFTER becoming big. You can't abuse power you don't have, and when Microsoft won the OS contract with IBM, it was a tiny company, and Apple was by comparison huge.
Microsoft got big by taking advantage of the fact that the guy that wrote DOS didn't think it was worth anything, so he was happy with the $50k (or whatever) that Bill gave him for it, and IBM didn't think that the PC market would go anywhere, so they didn't think anything of giving MS money for every PC sold.
When Bill started licensing DOS to every company that wanted to make a PC, Microsoft became big.
THAT is how Microsoft acquired the power to abuse that they then proceeded to abuse.