But you are assuming the result of the rewrite will be cleaner and have less rabbit holes. There is no reason to think that. If it is developed by the same organization it will probably end up with the same level of quality. Perhaps worse since it will suffer from second-system effect.
Indeed Netscape 6 was more buggy than any of the previous versions.
Doing emergency surgery on a code base and not knowing how many holes are left is likely to leave more rabbit holes than a rewrite.
Otherwise I agree with you. Rewrites are tricky. And the second system is particularly dangerous. But then it gets better - the third system tends to be a lot better than either of the first two.
Indeed Netscape 6 was more buggy than any of the previous versions.