Well, if you nationalize things and put state employees who don't give a shit in charge of them and production falls 1) that's not graft 2) that's on you.
Begging the question: why did you put a state employee in charge of production who doesn't give a shit about production and doesn't know what he's doing? What qualifications does this person have in the first place?
In this case, the answer is "none." You didn't appoint him because you thought he could run things, you appointed him because he -- unlike the person he replaced -- was loyal to you and/or you owed him a favor.
If, on the other hand, you nationalize the industry but leave the original employees and managers in place -- or better yet, encourage them to keep the surplus if they exceed quota as "profit", like they do in China -- you will probably avoid that problem.
Corruption, graft, nepotism, etc... these things are problematic no matter what kind of government you're running. Nationalization causes other types of problems (legally and political in terms of international trade) but that's not what's been happening in Venezuela. They're not having food shortages because of socialism, they're having food shortages because their leaders are greedy and incompetent.
So the massive oil profits aren't enough to skate by that anymore. When things get rough and it's time to get some actual work done, they're still fucking around playing house with the property they confiscated.
When the USSR broke up their privatization process was corrupt and created a lot of oligarchs, but those oligarchs had an incentive to produce things with those businesses.
Corruption by itself can lead to some pretty amazing things, actually (just ask Hillary Clinton) but even then is highly limited if those in power have a tendency to give power to people simply because they like them and not because they know what they're doing.
In other words, corruption is the process of wrongfully disenfranchising people, violating their property and their rights in favor of profit; graft and nepotism is the process of wasting that property and/or rights on people who have no business handling them in the first place.