Chavez expropriated a lot of private companies when he rose to power, mainly the oil companies. The direct consequence was a lack of investment in the country, both by international investors, as well as local entrepeneurs who shifted their investments to foreign countries.
All oil companies were ran by the goverment. Slowly, within a decade, production of oil was reduced significantly, mostly due to inept managers (who got their position for being supporters of the regime), and huge political corruption, who took the profit margins for themselves.
Now this sort of balanced out, when oil prices were high during the 2000's. But in the early-mid 2010's, the price of oil dropped internationally, their economy tanked, and with no investment from either foreign or local capital, they began experiencing a shortage of basic supplys. They tried putting out bonds and taking debt, but no bank would be crazy enough to loan to venezuela's corrupted goverment. Furthermore Chavez's death created a political vacuum.
Long story short, this is what happens when you apply socialism as your prefered system.
