The whole hoopla about browser choice in Windows was for much the same, as Microsoft used their OS market position to push Internet Explorer, that in turn pushed IIS.
Frankly the browser war was a proxy for intranet server competition. Netscape was trying to use internet tech to go after corporate networks, and MS was trying to cut them off at the pass.
You don't need to be a monopoly to get slapped with antitrust. All that is needed is for you to be the big dog of the pack, and seen as abusing that position.