They were a monopoly because there was no-one else in the race. BT's ownership of the local loop is also a monopoly. It's a monopoly because we can't go to anyone else to gain access to this bit of copper. The AOL Time Warner deal is quite different from either of these examples. For a start it is a merger.
Mergers go on the whole time in business.
ISP services, current affairs content and music are all available from myriad sources.