Why did Rubio collapse and Kasich surge after Super Tuesday?

[(Still) muted by Kalwejt until March 31]

Rubio's and Kasich's bases were actually different groups of voters.  I would argue that most of Rubio's support funneled to Cruz in early-to-mid-March.  Then, once a lot of the conservative Rubio supporters left for Cruz, his more moderate supporters left to support the actual moderate option (once it was clear that Rubio's appeal to all Republicans strategy wouldn't work).

-You can see this in North Carolina's and WI's primary.

[(Still) muted by Kalwejt until March 31]

After his disastrous performance in NH, Rubio recovered strongly by the time South Carolina came around and had by far his best performance relative to Mitt Romney on Super Tuesday. It's just that his best performance still was pretty bad, with him winning only Minnesota. After Super Tuesday, everyone saw he was unable to win his home state (assuming it was more favorable to him than Georgia, but less favorable to him than Virginia), and, so, was unable to be a viable contender. Kasich, meanwhile, was visibly competitive in his home state, and ended up winning it. That's why Kasich surged and Rubio collapsed after Super Tuesday.