In addition to the permissionless model as mentioned, another consideration is to standardize all the boring common bits. RISC-V incorporates a lot of industry

In addition to the permissionless model as mentioned, another consideration is to standardize all the boring common bits. RISC-V incorporates a lot of industry learning about how to handle extensions, compression, etc. If a company is considering RISC-V vs a proprietary design for an accelerator or such, getting debugged versions of those features in the ISA vs whatever gets cooked up in house in crunch mode could be pretty big.