ARM expanded upon the RISC-IV instruction set because it hadn't been updated since 1988. RISC-V was introduced in 2015, however if ARM hadn't been successful in the years preceeding that there's every chance RISC would still be lying dormant.

You're right that open source ISA's are generally better, and hopefully ARM will switch to RISC-V, but that really is a separate matter to ARM's viability under different societal systems.