What makes people be like this?

First I must agree, people are definitely like this and social media just makes it worse. I think it comes from a place of insecurity. And from a desire to feel good about themselves by being superior to others. Genuine friends and genuine good people are hard to find. Its possible to avoid people that behave this way (except for the occasion work or other obligation that forces you) but that can be isolating or at the very least make your world a smaller place. I think you have to find a way to not let it bother you. Thats the path to being one of those genuine people yourself. But not at the cost of your own well being. I find most people will talk themselves out if you let them go on about how wonderful they are... and then a more meaningful discussion can begin. But alas not everyone. Sometimes you just have to move on and avoid them...