Cruz is defending his stance because of what Trump said earlier in the campaigns about his wife and father. If that was still upsetting Cruz, then he shouldn't have spoken at the Convention, IMO. This just adds fuel to the fire of the Republican in-house feuding. We don't need that; there has been too much of it already. United we stand, divided we fall....GOP should remember that.
And maybe Trump did set a trap for Cruz, because I read now that Trump read the speech before Cruz gave it and allowed it anyhow.
But that is politics. If Trump set him up, Cruz still fell for it.