This is quite an assumption, and if it's true, it's only because those who disagreed with the regime have already been killed or leapt into the ocean to perish or prosper in Miami
It's not an assumption, there are polls with approval ratings for various political figures from even western institutions that show that approval ratings 40-60 are the norm. It's possible that the approval has decreased due to the crisis, but that's not unique to Cuba and if it is maintained it's plausible for the president to change.
I feel like I'm talking to automated talking points bots.
Please don't accuse me of being a bot just because my unstated priors are different from your unstated priors. It's really poor for the conversation and for every interlocutor.