Newt Gingrich realized that C-SPAN provided him a free 24-hour platform to talk about whatever he wanted on TV. He would go stand in the empty chambers and speak to the TV audience. It helped bring about the widening partisan divide we have today.
If you had basic cable, you got maybe 13 channels, one of which was C-SPAN, plus 3-5 local networks. Some of those would go off the air during the night. Others would be showing infomercials or bad movies or just whatever they had laying around. There was not a lot of competition at the time.
So if you were working the night shift, or an insomniac, or just up late watching TV for some reason, there was a decent chance that it would be one of maybe 5 things available to watch.
And hey, all those people get to vote. So if you want to influence them to vote a certain way, why not go talk to them when you're not really competing for their attention with anything else?