[johannes1234321]

Java's predecessor Oak was created by 13 guys (among them Patrick Naughton, Mike Sheridan, James Gosling and Bill Joy) over 18 months a different then relatively quickly grew to a larger team. (While that project didn't include the language spec itself only, but also runtime and library)

C++ wasn't designed by Stroustrup alone. It's based on C's design.

Sure sometimes you have cleared leaders (see also Perl/Larry Wall) but having a larger group has benefits to see more edge cases (with the risk of committee issues)