why are there so many assholes? why did humans evolve into major assholes?

You should know being one of them!

They didn't evolve, they were born that way. They began as a product of something that had to fend and fight for its living in order to exist. It was the way to be if you wished to survive , and that need has never left us. All the bullshit about 'Help ye one another' and 'Goodwill towards all men' is a delightful aim in life in which I would love to agree, but the harsh need to survive or perish negates that possibility of ever becoming the norm unfortunately. Get rid of the rose tinted spectacles, and look at the real world as it really is. Consider a simple thing like folk living without clean water. Countries who spend millions on weapons could cure this problem practically overnight by scrapping one missile, but do they ?

Like hell they do. To do so would increase the world population which would mean less for us, so the natural selection now taking place is perhaps thought to be the best solution.

Very practical and totally disgusting isn't it.?

Simply because we keep taking and taking from this world and we are too ignorant and blindsighted to see what we’ve become.

Because everyone has one.

Because humans evolved from deuterostome organisms.

Human anus is the first opening created during embryonic development (prior to the mouth!)

Because by definition, not everyone can rise to the top. Most of those who can't have some degree of resentment and they become assholes.

Because organisms' main objective in life is their own survival and reproduction according to evolution theory. Mammals in particular evolved with an alpha male mentality. This leads people to be egotistical little turds. Some believe they are better than others, some believe they must assert dominance in some way, others feel like they must be very defensive.