Everything you've listed is unique content, not oversaturated (that's secondary), and offering great value (vague). Many channels and blogs possess these qualities.

What distinguishes such channels is that they influence one's worldview, not just providing information but forcing one to engage one's brain while reading, provoking mental activity, and influencing identity formation.

The channel is in Russian. If you're interested and can handle the content using an automatic translator, I'll give you the name; it's not classified information.

As for your question about only 1.3k subscribers, the quality of the information presented is different and attracts a certain audience. Create a YouTube channel with cats and you'll have millions of views in just a couple of months, but the income from such an audience will be close to zero. This is entertainment content, while content about finance, which is specialized, attracts a certain type of person. It's probably the same in any industry.