What's the point of this if it's so heavily fictionilized?

It is also painfully slow and somehow convoluted at the same time, I don't remember ANYTHING from the first season because almost nothing was memorable. I don't know what's going on now either. So they include Charles Manson and the Tate-LaBianca murders, very fictionalized, but what's the point? When it's that far off from reality, just make something else. You might as well.

Right. It says up front it is inspired by historical events which tips you off that it is a fictional piece revolving around historical events.

Why do it? Well.... there have been many entertaining shows of this nature.

Also, fictional shows can help develop the back story of historical incidents. For instance, there is hardly any film of everyday Manson family life. But we do have written accounts of what it was like, how the family members regarded Manson, their group acid trips, and so on.
So any story about Manson family life has to be fictional to some extent, but it can still reflect the written accounts. Dialogue must be created though. Obviously nobody was recording their everyday conversations. A certain amount of creative license must be used.

Also, dramatic reenactment programs frequently edit or summarize the facts in order to keep the pace fast enough to entertain viewers. It's the nature of the business.
If they had cases develop at a realistic rate viewers would get bored.

that would have been great! I really like the non Manson parts of the series. I just know way too much about the real stuff to enjoy the heavily fictionalized Manson family in this show. I also do not get the point of some of the fictionalized family. For example they make seem as if the girls were not totally controlled by Manson. Another shocker is how much they changed the Dennis Wilson story line