"The entire world should use 2x more compute" is not a real answer. You can do that on your own personal computer which has compute to spare. For servers, you're already paying for the relevant amount of compute to serve your thousands or millions of users, and every % of overhead matters at that scale. You are suggesting everyone allocates a 2x budget for server-compute, or I suppose you're only talking about hobby servers where people are running tiny workloads and had so little traffic it doesn't matter?

A tiny minority of applications use a vast majority of compute.

If 97% of programs use 2x more compute, the total amount of compute used in the world will be nearly unaffected.

Large, well-optimized services are running at high CPU utilization all the time. But there's a long, long tail of services that are running well below 100% utilization almost all or all of the time, and it's not just hobby stuff. Vulnerabilities in those services are still real and can be very important, and trading some otherwise idle CPU time for an absolute shield against memory safety issues is a good idea. Even for some services that do have high CPU utilization it may be a good trade to pay for more CPU to get that shield in this new world.

2x PHP is still cheaper than Python and many other languages which most people would consider fine for your typical webapp.

Yeah I'd rather they spend 2x on compute than leak my data