Let me break it down to three basic steps:
1) Once upon a time, Venezuela were able to manufacture many of their essential needs. They exported what they have in excess, produce essential items that they need with their domestic industries, and import the high-end stuffs that they can't make themselves.
2) Chavez nationalized and destroyed all those manufacturing industries with draconian price caps that costs businesses much more to produce a product than they can make selling it. Manufacturing plants closed one after another, and Venezuela became reliant on imports to get EVERYTHING they need, using the windfall from oil sale, including all the basic essential items they were once able to make for themselves, like say, food and toilet papers. Why going through the effort of making it when you have the money to import it, right?
Consider this: Venezuela's agriculture industry was a net exporter of foodstuff before the oil boom. Now
over two-thirds of Venezuela's food supplies today are imported from other countries, such as Brazil, Argentina, Chile, Ecuador, Bolivia, Colombia, and the American Imperialists that Chavez and Maduro hates so much. In fact, about half of that imported food supply actually came from the United States. The few farms still functional in Venezuela are operating with ancient agricultural technologies and methods from, you guess it, before the oil boom. Even with the best harvests, Venezuela can no longer produce enough food to feed more than 1/3 of their population.
3) Oil price may be plummeting, but the real mortal wound is self-inflicted: Venezuela's rapidly-dropping oil production rate that is now a record
13-year low, thanks to failing machinery and equipment that have never been replaced since the glorious Socialist revolution, because Chavez just assumes they will run forever without fresh investments.
Now, the
Bolivares aren't worth the paper they're printed on thanks to hyper inflation, and the Venezuela doesn't have the money to import all those basic things that they needs anymore, and they are fucked because their farm lands lays barren and their factories are just hunk of rusted metal incapable of producing anything but rats.