I'm not actually sure why it didn't keep my interest, I think mainly I just never really cared about the characters. The plot wasn't any worse than some shows I've enjoyed, and I don't think the acting was all that bad. But I pushed through most of the first season on pure willpower. I watched each episode because I felt like I should keep giving it a chance, not because I really wanted to.

Then one day I realized I hadn't watched an episode in weeks, and I didn't care. I'm sure mister angry man goes on with his quest for revenge and kills lots of bad guys, probably in clever and dramatic ways. But I think I would have preferred if he had just died after a couple of episodes, then I would have felt some relief that it was over and I could move on to something else. Instead I forced myself to keep watching for a while, then moved on to something else anyway. Meh.