Isn't there something with VeriBlock spamming the mempool?
How many spams tx that they do? Are you saying those 400k comes from tx spam?
Truth to be told, daily transactions doesn't mean that much if the majority of those transactions comes from exchange/traders. No real usefulness there except speculation. Trading volume also rises to around 100k btc daily on a major exchange, maybe it's just a start of a trading wave.