If it is truly the will of the people, then they need to show up at their state conventions and make that happen. Because the primary only determines how a delegate is bound on the first ballot. It has been that way for a very very long time.
Trump supporters may wish the rules were different. But as long as they continue to be no-shows at these caucuses and state conventions, then they are doing nothing to change it.
At least Cruz isn't afraid to get his hands dirty. His people have been showing up and thwarting GOPe attempts to seat GOPe sympathizers as Cruz and Trump delegates. Cruz is the only candidate actually taking on the GOPe while Trump stands around and whines.
Those games are nothing but the old party insiders trying to have their way rather than recognizing the will of the voters as expressed at the ballot box.
It doesn't take a genius to recognize what is going on there. Rules, rules, rules. Nazi Germany had rules. Stalinist Russia had rules. Mao's China had rules. North Korea has rules.
Anyone who's ability to think and come to a conclusion about right or wrong ends with saying "those are the rules", well, they've told everyone a lot about themselves.