It's probably just for IP and talent acquisition, if I had to guess. People who can design high performance server-class CPU microarchitectures are rare.

Frankly, Ventana seemed like an interesting entry in the space, but I have no idea who would have actually bought their servers at the end of the day. They taped out multiple designs, but none actually seem to exist outside their labs. I don't really see any path to meaningful RISC-V server adoption for at least several more years and by that time Qualcomm could design something on their own, assuming they are serious about re-entering the market. Grabbing the talent and any useful IP/core design components makes the most sense to me, anyway.