In the case of Paige VanZant it is worth noting how little she was promoted at first.
The UFC decided they wanted booze in the TUF house more than Paige (she was under the legal drinking age) so they disqualified her from being on The Ultimate Fighter Season 20, although she qualified otherwise by virtue of being on the Invicta FC strawweight roster that the UFC bought en masse.
Paige's debut fight was buried on a UFC Fight Pass prelim, back when very few people had Fight Pass. So clearly they didn't do that because they had an intent to strongly promote her.
The way that Paige turned that around was to have such a rip-roaring battle with Kailin Curran that they got awarded Fight Of The Night despite the fight being buried where hardly anyone saw it. According to the announcers, however, they got a standing ovation from the live audience. Paige won that fight by TKO.
Apparently Reebok was impressed by the combination of Paige's youth, looks, and ability to fight and win an exciting fight, decided she fit a demographic they wanted to appeal to, and so offered her a special contract. With Reebok pushing her, the UFC got on board and started pushing her too.