You have no way of knowing how the Cruz people are switching Trump voters. If you have evidence of bribery, take it to the FEC. Bribery is a felony which no one should be accused of without evidence.
I do remember the Ford people complaining about Reagan doing the same thing in 1976. I know that you want to claim the high moral ground but this appears to be nothing more than procedural politics at which Trump has shown himself to be inept to this point. How is Trump going to deal with Putin if he can't handle Cruz? Putin is infinitely more conniving than Cruz.
And in all of those primaries did you ever hear a case where someone who was mathematically eliminated stayed in the race just to force a convention fight?