Cruz campaigned with Trump; that was that rally against the Iran weapons deal. That speaks for itself. I don't see what people's problems are when the one they supported is out campaigning with the President-elect.
Well maybe the unsubstantiated 'Lyin Ted' everyday on the Campaign trail had something to do with it or maybe the goldman sachs accusations (in hindsight, hilarious) or maybe that his father was involved in the JFK thingee, all conduct way out of bounds for a 'traditional' GOP Primary.
No one insinuated that Cruz doesn't share some policy similarities with Trump, Iran being one.