I've been thinking it had something to do with Valentine's Day, because one of my other accounts (dedicated to seasonal hubs) has been thriving while this account has been foundering. But the traffic has gone down from Valentine's Day and isn't picking back up on this account, so I'm not altogether sure what's going on with it.
Normally these things fluctuate though and eventually sort themselves out. It's possible that there was a change in Google -- though I haven't seen any updates related to that.
It should normalize eventually. Hubpages definitely still has a good standing because two days ago one of my hubs had almost 7,000 views.