Sometimes people start thinking that because they got successful in one area it gives them blanket check to talk about everything. Usually, the end result is they greatly overestimate their capability.
This is how many youtube channels die. The authors think they exhausted the topic and are looking to talk about other stuff and they start alienating their fan base because not only they are much less knowledgeable about those other topics, but also because the fan base just did not expect/appreciate those other topics. They came here because they liked the original videos and now the channel became something else which is unlikely to be what they wanted.
As for Sabine, I watched some of her videos on quantum physics and they were very interesting. Then I stumbled on one or two newer videos on other topics she started adding later and they were jarring, on the verge of misinformation/pseudoscience.