I think the internet has been "political" for longer than that. The development of blogging systems like Movable Type and then Wordpress in the early millennium gave rise to some extremely popular and vigorous blogs like Little Green Footballs. Some of these got so much traffic that suddenly their proprietors could live off the money earned just by casually sharing their political views (thanks to some affiliate links here and there).
The big political change of more recent years, I would say, is political discussion overflowing expressly political fora and contaminating pretty much everywhere because of how social media functions. A band or author will share some entirely innocuous, non-political post on their social media pages, but the comment threads below them can easily descend into a shitshow of partisan quarreling.