I mean, relative to IE, everything else was the alternative. Whereas in more recent years, keeping a closed-source rendering engine that was no longer competit

I mean, relative to IE, everything else was the alternative. Whereas in more recent years, keeping a closed-source rendering engine that was no longer competitive in implementing the spec, wasn't being used when people had a choice, and was being used as a dependency for core components of the OS, probably wasn't winning many arguments. (Edit: yes, I know Chakra was open source. I meant Trident.)