I'm so confused as to how that picture was anti-Semitic. Can someone explain in plain words how it was deemed to be that way?
Well, it comes from /pol/ apparently, so that doesn't do it any favors. But it's the combination of the star-shaped thingy over a bunch of money to insinuate that Clinton is corrupt from Jewish money. The shape alone is not the issue. It stems from a long-standing form of anti-semitism.
This is really just the straw that broke the camel's back. Trump has retweeted or spread messages that originate from white supremacist or neo-nazi sources before, and this is just one more example. His team needs to exercise to message discipline and vet the stuff they put out on his Twitter account.