The problem with Cruz dropping out is that if he did, the anti-Trump vote would have no distractions or decisions to make. You vote Kasich or you vote Trump. At that point, the establishment would not have to hedge their bets between the most viable candidate to stop Trump and the candidate they like the most.
The character of the campaign would change without Cruz, as would the news coverage of Kasich, who would become the candidate who had to be interviewed, discussed, and inevitably praised for his moderate views and electibility. Even (especially?) as a Trump voter, I'd prefer to keep Cruz in the race.
Cruz is only surviving because he is getting conservative support who still regard him as anti-establishment.
So, in effect, the establishment are running two candidates against Trump in order to keep him from getting the majority, since one can't beat him.