I'm thinking he probably was under the impression that Bledsoe was headed elsewhere.
Management made it clear that they were going after Bledsoe. Isaiah knew what he was getting into. He played it cool with his "it's all about the team" talk, but he always had his passive aggressive "I want to be a starter" comments. Hornacek tried to balance the backcourt and make everyone happy, even if it meant having Dragic or Bledsoe on the bench in the end of 4th quarter some games so Isaiah could finish. He still wasn't happy with his role.
Now Isaiah has fired his agent the same day he's available to be traded