Honestly, Steam is a tough nut to crack. I think the keys are to do well with the tastemakers (RPS et. al) to get a good initial burst of support; have a successful and strong launch (demo, achievements, launch at a good time, launch at an ideal price); aggressively participate in sales and build long-term momentum so that you become an evergreen.
I'm not sure that Shuggy did really any of the three. It got good feedback from many indie sources but never really broke through as a shining star, the launch wasn't particularly well timed--coming in that awkward pre-summer sale period--and $10 is on the steeper end for the game given its production values (although $10 is more than justified for the game), and when the summer sale did run around the dev went with a 50% sale + this summer sale was pretty shitty across the board in terms of actually promoting independent games, lacking the metagame that previous sales have had.
I don't think that's game over or anything, he count easily double his sales numbers with this daily sale, and hopefully get featured in future holiday sales... but still, I think it's pretty clear why things haven't gone better for him.