Let's not forget that the standards committee even suggests "behaving during translation or program execution in a documented manner characteristic of the environment" (that's the exact wording from the standard) as one of the possible outcomes of UB, and it's the one that C programmers are most familiar with and also the one most aligned with the spirit of the language.

Thus IMHO the blame falls entirely on the compiler authors for not making reasonable choices. The whole argument that UB makes for great optimisations is not supported by compilers like Intel's ICC, which has historically been much less likely to exploit UB, yet can generate far better code than GCC --- because it is much better at instruction selection/scheduling.