Before being used by everyone else Git was not used by everyone else.
Fossil is used for one of the most deployed embeddable database. Not sure we can call it "irrelevant".
I get what your message is saying, however words have meaning, and being hyperbolic does not help anyone when we try to bring nuances.
> Mercurial was a better DVCS [...]
Totally agree.
I think the massive difference is the number of people using the project vs. contributing to the project. How many people contribute to SQLite vs the Linux kernel. AFAIK not many for the former.