The idea that the Ferengi were going to be huge Star Trek villains remains laughable.
Star Trek: The Next Generation wanted to create their own show villain, much like how the Original Series had the Klingons. The folks on The Next Generation wanted to create a villain that was scary and who could serve as a series antagonist for the show’s length, so they created the Ferengi.
The problem is, they modeled them after the least ferocious people they could think of; lawyers and agents. They were designed to be small in stature and originally were heavily sexual. While the aliens were worked and re-worked prior to the start of the show, things finally came together and the whip-loving, flesh-hungry, bulbous-headed aliens that we saw in the Last Outpost came to be.
The Next Generation had no clue how to use them, and the idea of them being a huge threat quickly faded away, forcing the crew to go back to the drawing board and finally nailing the real series threat; The Borg.
Eventually, the Ferengi would go on to find a second act with the folks at Deep Space Nine, who took the race from a true threat to a minor and comedic annoyance. The tonal shift worked, and the Ferengi became centralized characters for the rest of the series.
The Ferengi were a bad fit for what Star Trek wanted.
Gene Roddenberry was very hands-on with the Ferengi, and really had no idea what he wanted to do with them. The very idea that Roddenberry outlined, approved, and then put this alien race out there for all to see is troubling.
The alien race was doomed to fail and if it wasn’t for the folks at Deep Space Nine, and to be fair, the later seasons of The Next Generation, the Ferengi would still be regarded as a monumental mistake that never should’ve seen the light of day.
If it wasn’t for Armin Shimerman being so engrained with the development of the aliens, as well as the character of Quark, the Ferengi would probably still be seen in a very negative light. Nowadays, however, while not the big bad they were promised to be, the race has turned into a fan-favorite one. Mostly due to Quark’s constant shenanigans and the lovable nature of Rom and his son, Nog.