A smart move by CoinBase indeed, and I do in fact see a massive sell-off of the currency in the coming days and weeks... as we can see already.
But, as I've mentioned before:
The Chinese and other smart investors knew that all the dumb money in the market was going to dump their Bitcoin Cash as soon as they were able to do so, then they will swoop in and buy it all up as cheap as possible... pure genius if you ask me.