With the block reward cut in half, miners are relying on Bitcoin (BTC) transaction fees to sustain themselves to a much greater extent.
May 10, miners earned 2188 BTC, May 12, this number fell to 852 BTC — a 61% drop. The halving of the block reward forced some miners off the chain, reducing the network hashrate. This in turn led to the increase in block interval, meaning that fewer block processed in a unit of time, decreasing the number of block rewards available to the miners.