And LLVM was bootstrapped by using GCC as the front end before clang was written to replace it. The freedom to combine with another program _temporarily_ while

And LLVM was bootstrapped by using GCC as the front end before clang was written to replace it. The freedom to combine with another program _temporarily_ while you bootstrap something better improves productivity significantly. And the world before GCC had a great many commercial compilers. Many of the crap. GCC replaced almost all the crap ones, so that only free compilers and a few commercial compilers that were good enough to offer something over GCC existed.