Venezuela isnt the only country to have operated capital controls like that and a fixed exchange rate.
I hope crypto gives a way back to a free market really I do for the peoples sake
In South America many countries have practiced several forms of capital and exchange control for obvious reason: they have suffered for decades from a total chronic domination by the US dollar and de-facto US puppet governments (or dictatorships) that have practiced policies to empower American companies rather than develop local industries (actually the destruction of entire advanced industrial sectors created in periods of independent governments is a recurrent thing in history of South America).
Americans always enforced an undeveloped industry in the continent, because they only need cheap raw material and workforce, so South Americans import high added value products, becoming more and more poor. Venezuelans buy Nike and Iphones, and sell raw oil: they will always lose. That's why the chavistas governments started a very long process of development, from free education to access to technology, housing, healthcare and incentives to creation of enterprises in the most needed sectors. Lifting millions of people from poverty is the basis to enlarge the productive power of an economy: more demand, more education, more access to the economy, more growth. The demand in Venezuela has skyrocketed, the economy has grown for many years, almost until 2011-13, also thanks to the high oil prices and despite the continuous US aggressions. These development policies are considered hostile by the US.
In this condition, local currencies are obviously extremely weak (the levels of inflation in many Latin American countries are very high, even without an economic crisis).
People try to create savings by buying USD. Mostly rich people export endless streams of capitals that end in US and European banks or tax havens. This has led many governments (not US puppets) to create some sort of exchange and capital control, with some exemptions for companies that need to import. Of course this is not ideal, but it's a measure that comes from weakness, not certainly because people in power like it (also because it's unpopular). It obviously might not work and create the opposite effect, through the black market: an inflation spiral as you say.
BUT.
This is absolutely not the main problem in Venezuela: the situation is WAY more complex than that. The capital control is only the thing opposition supporters keep repeating obsessively to attack the government (it's an opinion among others), but any change in exchange controls is far to solve the many problems and even the hyper-inflation, which is caused by other manipulations of the market (mostly an arbitrary criminal exchange rate established arbitrarily from Colombia and Miami, called DollarToday). If it was so easy to stop the inflation, the government would have done it.
The Petro could help, but it will take time. They are doing many other things to face a situation of "dirty war" that is currently unique in the world, and needs innovative and creative solutions.