AoS is known for being a show which did WAY better in streaming than live. Those live ratings you quote? Yeah, AoS more than doubled, sometimes tripled those numbers within three days, and that is not counting all the people to get to it within a week or waited until it dropped on streaming. That's because AoS isn't really a good show for live TV, since the show works of the assumption that the audience not just watches every episode, but also remembers what happened in the show five seasons later. It's exactly what I love about it, but it lead to a lot of people preferring to stream it instead of watching it live. Didn't help that sometimes AoS had an extremely erratic schedule, especially during its first episodes and in 2016, during which there were constantly episodes not shown in some areas due to the elections.
Nielson numbers only provide half of the picture nowadays, and they are an outdated system to truly measure the popularity of a show. Like I mentioned, once they looked into streaming, it turned out that AoS is one of the most popular and most watched show worldwide. Which is exactly why they keep the show going.