More than anything else Vito wanted to protect his FAMILY. If he had returned to full health and found out Carlo was brutally beating Connie -enough to send her to the hospital - he would have given the order to have him whacked himself.

And Sonny was his firstborn - had he found out that Carlo was complicit in Sonny's hit, if he was physically up to it, he would have done a "Fanuccci" on Carlo himself.