Because all conspiracies have some truth.
Say, Muslims want to hire only Muslims because they share cultural traits. Trump says the country is Christian, meaning, he's pushing Christian values.
Why would Jews be any different?
Our side of the world is very Christian-oriented. We don't notice it because we live in it and we're used to it. For many Muslims and Jews, it feels foreign. Many Jews communities have no idea who Jesus is, do not celebrate Christmas, and even celebrate New Year differently. This has made them "tribalists", as in they gather among and with their own community only. When they have power, they also look to share and push their own values and surround themselves with their own people.
The fact that people think this is some sort of "racist conspiracy" is r/etarded. It's human nature. Of course, some are supremacists and want to get rid of those different, but they aren't many.