Rubio was calling him a liar because he didn’t speak Spanish. He wasn’t giving a speech, he was just making Rubio look like a fool.
There's a non-zero probability that Rubio trolled him into speaking Spanish because he understands the optics here better than Cruz does.
There are reasons why a squish like Rubio won't be hurt by his globalism while a supposed hardline conservative like Cruz will be.
This is advanced optics. Not for rubes.