If a entire country need to borrow a paltry 40 something million i would call that a bad investment on russia’s part...unless they are counting on a default.
Cuba is cheap outside tourist sector. I think average salary is like $10 a week and $1000 buys you a house.
A default would be a good play if the collateral was “right”. If the collateral was REALLY (i.e., planned, as you surmised) right it could be a VERY good play.
Somebody will be getting their pockets nicely lined.