You're right and Cruz was unbelievably good!
However, how Trump has changed this is he brings ratings. If he sits out a debate the ad revenue is nothing. If Cruz sat out a debate all the rino's would try to take advantage of it and go ahead with the debate.
What I'm hoping for is some good business sense gets interjected. The top 6 candidates should do the debates themselves, buy the TV time, sell the ads and split the profits or give them to charities. Shift the power away from the party and "objective moderators".
The idea I saw floated was for two debates, with seven randomly selected candidates in each. Strikes me as a weak platform, but the leading candidate need the lower ranking ones united with them in a show of solidarity against the RNC.