there's winners and...

why so, I was taught that plural nouns take the "there are" form and not the other way. Even though I've seen "there's winners and there's losers" over and over. IS THERE an explanation for this?

In colloquial speech people often use "there's" instead of "there are" though it is grammatically incorrect. In formal situations you should use "there are"

Because "winners" and "losers" here are treated whole as singular nouns, not plural.