not so much "broke" as "fixed"
IIRC it was incompatible with other compilers due to bugs, and at some point the time came to fix them, otherwise the state of "incompatible .so files based arbitrarily on which compiler you used" would have remained there, permanently.
but yeah, such fixes are painful and unfortunate
on the good side, they offer opportunities to fix other problems that would be a permanent maintenance burden, but that the ABI barrier enables tools to overcome