It sounds like you don’t understand the difference between the words “majority” and “plurality”. You need a majority of delegates to win the Republican nomination, not a plurality of primary votes.
Cruz has no chance of getting that number and should drop out, as should Kasich.
When a candidate recognizes that he cannot reach the number he doesn't plot to keep the frontrunner from getting it so he can fight it out in the convention.
What Cruz and Kasich are showing is their own lack of character and are ending their own future presidential hopes.