There isn't anything super special about Bootstrap. I don't know the people so I don't want this to be construed as opinion about the people who develop this, but it is my opinion that Bootstrap does not require top talent.
Bootstrap set the stage for responsive CSS framework. It's easy to look at it these years later and say it's not that impressive but that's ignoring the context in which it was built.
Yeah, but it does not require impressive engineering (as in requiring super brilliant devs to get it done). It is mostly a good idea followed with a reasonable execution.