It gave him a sudden boost of visibility and to his sales for sure, but it hardly "launched his career". Sanderson was already one of Tor's "up an coming stars" from the new generation of Fantasy writers with his Mistborn trilogy, one of their writers they found most promising. The success of his own novels and their steadily growing fandom actually made Tor a little worried that he would put his own career on the backburner for WOT, and this is why Doherty pressured him to finish Way of Kings in between the two WOT books, as it was all Brandon had advanced enough. Most of his notoriety and critical acclaim in the field outside the WOT fandom he still gets from his own novels, not at all for his contribution to WOT.