You said if it was on Netflix it'd blow up. I'm just proving that to be incorrect as both HBO and Sky (in the UK, as you say) have huge viewer figures and plenty of shows that have exploded in popularity, quite recently too, like Mare of Easttown. There's nothing to suggest that it would be different on Netflix. Lots of really good shows have gone under the radar on Netflix too. Most of what gets really popular on Netflix is actually shite liKe Bridgerton designed to appeal to the masses rather than tell a great story.
I know loads of people who've seen Succession, I actually watched it because a friend recommended it to me. I wouldn't call it underrated or low profile, it's not the biggest show on TV or anything but it's still popular and has swept up awards and gotten massive critical acclaim.