Do you need to have a big ego to be an investor?

I have had an experience for a long time now with one investor who for the most part is your perfect type of investor (silent and then helps when required). However, the only problem is that they tend to over inflate their involvement to everyone they know (even to the point of flat out lies), which then end up making their way back.

Why?

Why can’t some people just be happy with what they have? Why can’t they simply say they have got the best investment of their lives and they didn’t even need to do anything apart from be in the right place at the right time with a little bit of money at Seed stage?