I'm not surprised he's having a good first week. He promo'd a lot and was always the most popular member of 1D. This isn't the end, though. What will sustain sales? It doesn't matter if he has a good debut if he drops like a rock. Because hype isn't going to sell albums in the long term.
It's too soon to be making definite, absolute judgments about the success of this project and the success of 1D guys in general. Stop the triggerhappy stanbaiting comments. Let's try to take a nuanced approach.
I'm curious to see what they'll push as his second single.