And yet the block keeps expanding, so clearly the powers that be feel that the ratings they're getting are still better than anything else they could put on at that hour. Or even more likely, they don't really have any expectations for that hour either way, because, y'know, it's 3 in the morning on a Saturday.
Honestly I have no idea why any of you are sitting here in the year 2017 giving any sort of credence or inherent worth to hideously-inaccurate and increasingly-outdated Nielsen statistics, numbers that don't even pretend to properly take DVR and streaming viewers into account. Just watch the shit you want to watch and let the people who are actually paid to worry about that shit do so.