Except that dozens of 'humorists' joked over the past few years about the KNOWN floating garbage problem of Puerto Rico, which had been in the news and everything.
So he did not steal the joke, he simply had the audacity to tell it near presidential election time when the permanently pearls-clutching and endlessly virtue-signaling Political Left could leap on it, falsely claim it was racist, and pin the joke itself on Trump.
This is one reason why the Left's very own Jon Stewart defended both the comedian and the joke afterwards . . . while the Political Left pretended he never did that.