Halloween has its own smattering of licensing challenges (more so than Nightmare) which always made that rumor feel somewhat unlikely. Chucky is marketable, but there are likely maintenance expense concerns with an animatronics-heavy house running year-round. Friday the 13th, while absolutely marketable and synergistic with Crystal Lake, is in a weird limbo because of that synergy. It also has, admittedly, the most limited environment of the Titans.
TCM, arguably not in the top three, fills the slasher (and gore and chainsaw) house role. Legacy also demonstrated how expansive Universal’s permissions for IP are, even if they don’t focus on the movie. That movie, also, is celebrating its 50th.
But really, I think a big reason they went with TCM is… simply… Texas. Vegas is very popular for Texans. It’s easy marketing to a big market.
Exorcist Believer is a sunk cost.