I believe it is a natural cycle in which we get less players for a while, and later on we rejuvenate once again. Many players have become afk due to their own personal things, or because the game has become less enticing to them than it used to. I suppose than in a few months the tide will rise again and we will receive plenty of new players eager to play the game.
Also, toribash is a difficult game. The learning curve is incredibly steep, and many players have just given up on it because they wanted to play it and be good in a short amount of time. For example, I told a friend of mine that he should play toribash with me, as we usually play many games together (not casual games per se), and that I'd teach him (the basics, as I'm rusty as hell). In like 30 minutes, he just gave up.
It's a combination of factors that will always make this happen at one or more points at a year.