This is exactly why ASIC-resistant algorithms like RandomX were invented. Bitcoin uses SHA-256, which is only profitably mined on specialised late-generation ASICs, made in one country that has a fraught relationship with both Bitcoin and its neighbors. If they (alone) wanted to, they could commandeer and build-out enough hashing power to launch a 51% inside twelve months. If they got together and decided to collude with their frenemies on the Potomac, they could do it today. RandomX (and a few others like Ghostrider) are only profitably minable with general purpose CPUs. There are a boatload of those out there (compared with the number of SHA256 ASICs), and a (small) number of countries able to build them. It doesn't entirely prevent a 51%, but it both sets the bar higher and gives others a better chance of countering such an effort.