It sold 1.35 million for GC's ~22 million userbase, how much do you think it's going to sell to Wii U's smaller userbase? Especially considering, that horror games, like REmake, RE0, RE4, and Zombie U, have never sold as well on Nintendo platforms as they have elsewhere.
RE4 sales doubled when it went back to the PS2, and RE5 sales more than doubled on the PS3 compared to the RE4 sales on Wii, eventhough the latter had a larger userbase.
The REmake is clearly made for a new audience, and platforms where it's likely going to sell better.