How did you come to the conclusion that 750 people is a lot to build a web browser? The Chrome-adjacent teams at Google are about 4,000 people, and that doesn't even include all the people at Google providing infrastructure (e.g. servers, workplace, HR, legal etc.).
Comparing Firefox to Chromium-based browsers doesn't make much sense since these browsers don't develop their own web engine.
Comparing Firefox to Chromium-based browsers doesn't make much sense since these browsers don't develop their own web engine.