According to Mastercard’s CFO, Martina Hund-Mejean, the downward trend is an indication of the “recent drop-off in crypto wallet funding”. She elaborates:
“What the issue is that a number of the banks have decided, in particular in the United States, that they would not allow the usage of cards for this particular funding vehicle. And that’s why we have already seen a relatively significant decrease of the volume related to that event.”
https://news.coinninja.com/blog/2018/05/03/master-card-feeling-the-effects-of-bank-credit-cards-banning-crypto-purchases/Very cool to see credit card CFO's discussing crypto.