The Venezuelan economic collapse has been caused by multiple factors. The chavista regime took over in 1999 when oil prices were in the low teens, but soon thereafter they climbed above $100 per barrel, and even this year they are averaging about $40 per barrel.
Therefore, the oil bonanza encouraged Chavez to destroy the country's productive capacity via nationalization, excessive regulation, price controls, and extreme corruption.
The nationalized properties were wrecked and today they are non productive. Education began to suffer, and the justice system fell apart, leading to a huge crime wave. Government repression has upped its game and since 2014 they have murdered or imprisoned hundreds of opposition leaders and protesters. This in turn has driven a mass exodus of middle class and educated Venezuelans.
To compound matters the Maduro regime is essentially a puppet of the Castro dictatorship, which had enjoyed a huge windfall taking money from Venezuela. Lucky for Raúl Castro the USA elites have decided to help him survive and are steering business and cash in his direction. Thus Venezuela's misery is in part sustained by a Castro repression machine which is in turn aided by Yankee elites from both sides of the aisle.
As you can see this is a fairly complex story, it's not useful to simplify and only blame socialism. This tragedy goes much much beyond what one can blame on people like Bernie Sanders. It's a tragedy which causes enormous pain and suffering, and there's a lot of blame to spread around. But, as long as Obama smiles at and cozies up to Raúl Castro, the rise of communist dictatorships in Latin America will continue.