I don't know if that's still the case, but last year the government set his own rate for bolivar to USD conversion inside the country. Rates which are of course only realistic in fantasy land. The only alternative was the black market, with all it entails.
There are probably heavy controls on the import of foreign currencies.
That makes sense... Cryptocurrencies might have helped there, but with how hard they are to use and with how impossible it would be to actually exchange them to and from fiat, they'd practically be no help at all.