I've always rather liked - and found quite credible - the anecdote about the leaders of the Cuban Revolution getting together for at the first planning meeting after the fighting is done, and Fidel says "Is anyone here an economist?" and Che is pretty bushed and half asleep, and he thinks Fidel said "Is anyone here a communist?", and he sticks his hand up.

So Fidel gives him the job of getting the economy running right, and that's how the Cuban Revolution moved to the left.

But the thing that really drove Cuba into relying on the Russians was, of course, the way the USA pushed it away and set out trying to undermine the new government. And has kept on doing that for the last half century.