He wanted out because he was unhappy with McHale, see link below. And as mentioned Dragic signed with Suns before Lowry was traded and Dragic only signed with Suns, because the Rockets didn't agree to terms with him, so Dragic wasn't an issue any longer. I think they traded Kyle because he spoke out. http://blog.chron.com/ultimaterockets/2012/05/disgruntled-lowry-feels-its-his-time-to-move-on/
Toronto is a great city and lowry is a philly dude,so i dont think the snow will bother him much. Once they lost dragic, i thought lowry would be back, but if a team like toronto offers a potential lotto pick,they had to take it.