RIP Sumo. Dumbest decision ever and ever... Greedy bastards. Bitmain involved 100%. Gave some cash and devs fucked the loyalty.
From the last 2 posts on their blog I suspect this is more because they are afraid Fireice will attack their network. I think they've panicked and switched back to CN to archive bigger network hashrate to prevent 51% attack... Still worst decision ever. They are ruining their coin anyways due to huge drop in exchange rate & volatility.
As you noticed... the coin was under attack. I assume it was a last call to save the project. And frankly... it worked. Of course a lot of people sold in panic. But as usual... panic and fear are bad advisors.
The future will tell if the coin manages to recover....