I figured it out by waiting until the goat moved but I still don't know how to beat them normally now that there are a bunch in the levels. Is there something I'm missing?
I'm going to redo the goat boss in a later update, so that players don't just have to wait and avoid it, but nope, you're not missing anything. Right now, the goats are only defeated if they jump into spikes. Have fun with the rest of the game!