I think Cruz is letting Trump entertain The People and build momentum for them wanting to select a Republican president. I hace a feeling he will begin to get more active and outspoken as the election draws near. He may be letting Trump burn himself out. I guess we’ll see.
20 months of any presidential candidate is going to cause people to tune them out. This is a good time to let Trump play the clown and then re-engage the public sometime next fall.