Olympic Arms folded in 2017 too. IIRC, Colt no longer makes ARs for civilian market either.
The market is good and saturated with AR makers. It's not a shock that lots of them are going under, but is kind of surprising to see the big names going away. It'll even out with Daniel Defense, LMT, LaRue, POF, LWD at the top of the market and Smith & Wesson, Diamondback, ATI, Palmetto State picking up the mid to lower range markets. I don't know how well they're selling, but I wouldn't be surprised if Springfield takes the SAINT and gets out too.
ETA: and that's still quite a few!