Bad raitings (or not good enough), internal conflicts like the ones that kept cancelling Yost's Shared Marvel universe? Or simply someone with the power deciding not to continue it?

I can count two times where the DCAU could've continued after JLU, One was the Supergirl and the Legion of Superheroes backdoor pilot that was picked up by KidsWB as the unrelated Legion of Superheroes (some say that this was because old men thought that no one would watch a superhero cartoon with a female lead) and Justice League: Crisis on Two Earths which was adapted from a DCAU Movie script by Dwayne McDuffie that was supposed to bridge Justice League and Justice League Unlimited.

Why wouldn't they just set it in the DCAU? The movie in particular, was practically the same with an ending that almost directly references the formation of the JLU, all you have to change is the Green Lantern and the fate of the Martian Manhunter. I just don't get it.