“They got beat” sounds like American slang (I speak English english, no offence intended). “They were beaten by. . .” sounds correct to me, but sports pages speak their own type of language. If enough people use words in a particular manner for long enough then they will become be recognised as correct, and in a colloquial case it is already correct, but it is grammatically incorrect right now.
I’m with you guys! “We got beat” makes me cringe. Even though I expected some decorum in my classroom, I had rather have heard, “We got our asses kicked.”
Just this week I read the words of a minister who claimed that stores were being brow beat into saying “Happy Holidays” instead of “Merry Christmas.” (Double cringing and gnashing of teeth)