tl;dr: Meh growth, but "exponential growth" on the current small scale for March. Spike of interest based on some PR news without any substance. An Ethereum agency selling snakeoil and big-gov-money just wanting innovation-news-credits for "taking advantage" of the latest hype around blockchains without really understanding anything about it.
If you don't take into account a big part of March, I don't see any exponential growth. I think it's just piggy-backing on Bitcoin's danger of a hard-fork and recent drama. In general the numbers are so low that any kind of spike looks huge.
Another factor is the latest PR on a Ethereum-related consultancy getting a governmental contract on Dubai for smart-cities etc. However, I have talked a person that is involved in that and everything was just a google doc, there is no substance behind it, plus the Dubai-side just want something related to the blockchain-hype without knowing a lot about it.