One of the big differences was in attitude. The TLS 1.3 anti-downgrade feature was not compatible with some popular middlebox products. Google told people too bad, either your vendor fixes it (most shipped free bug fixes for this issue, presumably "encouraged" by the resulting customer anger) or you can't run Chrome once this temporary fudge goes away in a year's time.

Previously (in earlier protocol versions) nobody stood up to the crap middleboxes even though it's bad for all normal users.