The will of the voters was quite clear. Cruz + Rubio > Trump.
Even if you choose to interpret the results that way, that's not the way most people see elections. Most elections in the US are done on a First-Past-the-Post basis, it's what people are familiar with.
If Trump finishes with far more votes and delegates than Cruz, he will have a far stronger narrative going into the convention, and almost certainly have greater public sympathy for his case. I think Cruz will look like he is trying to overturn the will of the voters based on sneaky backroom deals.
Also be aware, I'm not arguing over what is actually happening, or the ethics/morality/legitimacy of it, only how I believe it will be interpreted by voters; two very different things.