Cruz's plan is simple. He's not stupid, he knows it's either Trump winning or a brokered convention at this stage. His plan is to knock the others out now so that he can a mass the second largest number of delegates going into the convention, and be the clear second place person to TRump (rather than having multiple contenders all with 100+ delegates).
Rubio losing Florida and Kasich losing Ohio means that:
1) If Trump wins, then Cruz was second place and the clear runner up, so he will get the nod in 2020 after Trump explodes in a general. He can campaign on being a real conservative and the reason they lost under Trump was because he was a fake liberal.
2) If it's a brokered convention then he'll be in second place. That might give him the nod as a compromise agreement if he chooses someone like Kasich or Sanderal as his VP. More importantly, it makes it very, very hard for any of his current rivals to be chosen as the nominee ahead of him.
3) If it's a brokered convention and he isn't chosen then he gets to do 1) - run again in 2020 as the favourite to win.
Cruise isn't stupid, he's built the best ground game out of all the republicans and has been sighted on the way to win for a lot longer. Whilst I'm sure he'd love to get the nominee now, a lot of what he is doing is about preparing for the future and potentially 2020. In order to get any of that done, he needs Rubio to lose in Florida ASAP. It's better for Cruise that Trump wins Florida and wins the nomination than it is Rubio to win Florida and then stage a comeback that puts him in second place in the convention.