Complex sentence: ESPN2 was initially formatted as a network for a younger generation of sports fans; by the late 1990s, this mandate was phased out as the channel increasingly served as a second outlet for ESPN's mainstream sports coverage.
Split into simpler sentences: ESPN2 was initially branded as a network for a younger generation of sports fans. This mandate was phased out by the late 1990s, as the channel increasingly served as a second outlet for ESPN's mainstream sports coverage.