Small groups of fans can become large groups of fans. They also can remain small groups, or even diminish. And the general principle of everything is that successes are much more rare than failures, and the majority of media that didn't catch immediate attention will... just die unknown.

If you gave a chance to every movie that might become popular, you'd be throwing huge piles of money on nothing. Which is not the best business strategy

And you shouldn't be quick to throw shade on people whose entire job is to manage their business. Finance department people who do nothing but calculate which metrics exactly the show needs to hit in order to be worth it. I mean, I'm not gonna say that the business doesn't make mistakes. Businesses make lots of mistakes, and sometimes quite stupid ones. But yes, unless I see some kind of evidence of the contrary, my default assumption is that these people are competent at the jobs they were employed to do, and that the decisions they make are sensible

They most likely define success as views and retention. I haven't seen the metrics, but my guess would be that most shows are "a small group of people really likes it but it doesn't draw the larger audience and as such doesn't pay for itself". Yes, a show does need to have a large audience to exist, otherwise it's a waste of money. No, the fact that you personally really really liked it doesn't make it "successful"