If you're looking at volume in terms of US dollars, then of course the volume crashed due to the fact that the prices of all the coins crashed (meaning that they're going to look like they have less volume in USD) If you compare this to the amounts of bitcoin they have volume in, it's not much of an issue at all -- check out this reddit thread for more in-depth explanations on the topic (https://www.reddit.com/r/kucoin/comments/7rp089/volume_on_kucoin_what_happened/)