Conservatism only works by having a consistent ideology and sticking to it. Too many conservatives are adopting left wing thought patterns. Conservatives are supposed to be for the Constitution and the rule of law. Are you saying that conservatives were unfairly attacking Obama back then, or Cruz is doing something he shouldn't know?
Obama was negotiating with the Iraq government concerning the terms of withdrawal. And he was negotiating a policy that was counter to the legitimate Bush administration.
That would seem to be a violation of the Logan Act.
Cruz is having conversations with foreign governments regarding their situation, apprehensions and aspirations. There is no evidence that he is negotiating anything or acting counter to any established American foreign policy.
I.e., there is no violation of the Logan Act.
Which is to say that criticism of Obama in 2008 and approval of Cruz in 2014 is neither being inconsistent or hypocritical.