A huge hash-rate mined a lot of blocks very quickly, and then left, leaving the difficulty extremely high
Although the global hashrate shown by the pools has not budged for some days... so something else is possibly happening too
I have found working difficulty graph at
http://fbf.fastpool.eu/ and I can conclude that this coin is under attack since 10th of May. Not sure why people are doing things like this. But they should lost interest in few days I think.