I worked in and studied election history/outcomes for ten years. About
half of registered voters in the country are Democrat and about one
half is Republican. Independent voters determine who wins and
Independents tend to not vote in any primary/caucus, they vote in the
November General Election.
Subtract registered conservatives who will not vote for Trump, subtract
more Trump votes because he has high negative numbers in the general
population (these are the Independents), and Clinton becomes President.
Cruz does not have high negative numbers in the general population like
Trump does so Cruz gets most of the Independent voters along with
conservatives, and Cruz wins.