Why are interviewers rude?

I am an experienced guy and had a couple of interviews recently, where I observed that the panelists were extremely rude.

I could understand that my answers did not make much sense to them, and I am happy to accept that I am not a 'mr. Know it all" but their rudeness is not clear to me.

As far as I know I did not say or do anything to offend them, and the point of interview discussion is precisely to find out how much a candidate knows .

Could you help me understand What might be the reason for their arrogance?