I don’t see any thing in there as really negative...Cruz is after all an opponent...I think Cruz is wrong about Trump...But Cruz has to sell himself first to his donors...And that’s what he’s doing...
If you read Trump’s books, the most likely scenario is that Trump will respect this sort of move by Cruz.
Also, it wouldn’t surprise me if Cruz either leaked, or had a hand in leaking, this video himself.
Doing so gives him a great deal of freedom of political movement. The most people can accuse him of is playing politics. Which is shocking when done by a guy running for, you know, President.