Mostly because it had a garbage engine. The one they used in the movies was modified with a much better engine.

it wasn't a good car, It just looked unique.

The suspension had to be raised to meet new pedestrian safety standards. This ruined the handling.

They couldn't get the engine they really wanted (a Mazda rotary) and had to go with a GM piston engine instead. Then, new US emissions standards hit and it had to be downrated to meet those. EU models were better, though engine design in general was kinda in the shitter around this time.

People think it's heavy because of the stainless steel, but those are thin panels over fiberglass. Its weight is in the same ballpark as what Ferrari was putting out at the time.

The first alternator they used did not have enough power for all the accessories to be on at once. People got stranded at night because of this, including Johnny Carson (who was an early investor). These were upgraded later.

Then there's some manufacturing difficulties. The early models have creases embedded on each side of the hood. Forming the stainless steel that way often broke it at the factory. Later models have a completely flat hood.

As the company's finances dwindled, DeLorean himself was caught in an FBI sting operation where he was accused of selling drugs to try to keep the company afloat. This ended up being a setup by the FBI--with Larry Flynt coming to the rescue, of all people--but it plunged the company's reputation even more.

It was a shitty time to make a sports car. Lots of stuff happening at once that made them bad at what they are. Make it 5 years earlier or 5 years later and it's an entirely different story. Even that might be generous; 1980s sports cars are known more for their angular looks than actual driving ability. It wouldn't be until the 1990s that companies started to figure out how to work within the new regulations. Then you get legendary bangers again like the Supra MkIV.

It wasn’t hated. It just wasn’t a good car.

You misspelled Mandalorian