Someone took a picture of him working at Target and it spread like wildfire because white gorls are crazy and obsessive over the simplest of "men". He had around 2k followers on Twitter before and now he's up to 373k. "#AlexFromTarget" also trended WW.
He's not ugly or anything but he is literally only "hot" from that angle, in that lighting, with his eyes closed/down. And now there are thousands of tweens writing fan-fiction and tearing down old posters of 1D and Bieber just to find room for him on their wall.