Wha? I have no clue what is the profile of the average Gab user, but ..nazis? Seriously?
The same reasons why bitcoin gold, bitcoin diamond, bitcoin platinum, bitcoin shit and bitcoin super craig shit exist...
Everyone wants their own browser/coin and they do this either for a moment of fame or in most cases because they smell a load of $ coming their way.
It is actually based on Chromium, which is also the base for Chrome, small and big difference at the same time