Well, OK. But by that logic, if the language they had been most familiar with was Fortran, should they have used Fortran for Facebook? I tend to think that there are actually material differences between languages and technologies, and it's worth knowing more than one language and not using terrible ones.

“ But by that logic, if the language they had been most familiar with was Fortran, should they have used Fortran for Facebook”

Absolutely. Otherwise they wouldn’t have been able to release the actual product and keep adding features to it the way they did with Facebook. They’d spend half the time learning the “right” language & environment. That would have slowed them down to the point they wouldn’t have been able to work on the actual product as much as they did.

And feature-wise, Facebook evolved really quickly.

That just sounds like "they succeeded because they knew a programming language", not that it was right one compared to competition

No, they totally succeeded because the used php. I think zuckerberg said it himself that php allowed them to add new features easily. I think he mentioned that it was easy for new people to pick it up. I’m pretty sure Facebook wouldn’t exist today if it had been written in the more corporate/esoteric languages available at the time.

Its ease of use allowed him to launch the site from his dorm room. Iirc, YouTube was also written in php (it had .php urls), before google bought it and rewrote it using python, so you could probably thank php for that site too.

Just checked. It appears it was indeed first written in php then changed to python then to java.