x86 is an Intel standard; they own the patents. Some of the patents have expired at this point but there's new ones which you would need in order to make a comp

x86 is an Intel standard; they own the patents. Some of the patents have expired at this point but there's new ones which you would need in order to make a competing x86 processor. x86_64 is an AMD standard, I believe still under patent. Intel and AMD cross-license these patents to each other. As a result, any other company wanting to make x86 processors would have to purchase rights from both companies (assuming they're willing to, which is a big if), which would instantly make their products cost-uncompetitive.