Why Was Season 1 So Short?

TFTC's first season was a mere six episodes long, whereas the subsequent seasons have much more. I wonder why it was so short? If I were to guess, I'm guessing HBO decided to test the waters to see how the show would fare with ratings and if it was successful enough to not just renew it but also increase the budget and allow more episodes. I know Horror hit a bit of a dry spell in 1989 with the many Horror film sequels at the time that burned out so many, so perhaps with the slightly declining popularity of Horror at the time HBO saw TFTC as a bit of a gamble and decided to wait and see how the first season fared. When it was not only a big ratings success but was also critically well-received, it was a no-brainer to renew it and also increase the episode count.

It's not the only time a Horror TV show had a short first season either, The Walking Dead's first season was also short (I think only six episodes as well), and when that ended up being a big hit more episodes were greenlit for the second season.