Because you are dependent on KS to survive. Launching another franchise would have given them an opportunity to grow and fund their own ideas in the future. Also, and I know this may be harsh to say, only surviving is a good way to lose your best employees.
The biggest thing, as I mentioned before, is that I think that they wouldn't be able to reach 4 mil this time around. Although chances are that they don't need 4 mil to make PoE2 as all the ground work has already been laid out with PoE1.