Explain that to the Kasich voters. I’m pretty sure voters in Indiana, South Dakota, Nebraska and other non-Trump states will still vote for Cruz knowing as long as Trump doesn’t get to 1,237 on 1st ballot, Trump isn’t the nominee.
If Trump is within 100 or so delegates then Trump will make a deal with Rubio or Kasich to be the VP and take his 100+ delegates to obtain the nomination.
Kasich isn’t pretty and Rubio is a squirrel but if it gets the nomination it may be necessary
Fantasy/Hope
Then the demodogs will challenge Rubios eligibility and he will be forced to withdraw. Trump replaces Rubio with a better option