They had lost out in the first round of the playoffs two years in a row, each time to very good teams (the Washington Capitals and Boston Bruins), and there was a consensus around the hockey world that this was a skilled but young Leafs team that just needed some time to mature.
That summer, they signed John Tavares. It would be dramatic to say everything changed, but the expectations did ratchet up significantly. The team suddenly had a star in his prime surrounded by a collection of elite young talents. They went from a fun but young team to a club expected to win.