I think a lot of people believed her lies. Trump certainly found her useful.
Powell is a highly accomplished lawyer, and not a stupid or deceitful person.
What she said is that she had a huge volume of leads, "like trying to catch water from a fire hose" the volume of leads reported to her, that she did not have the resources to investigate all of them herself, and therefore not conclusive. But certainly, enough leads to warrant a large-scale investigation of a massive conspiracy to rig the Nov 2020 election. And from the opposing side of Dominion Voting Systems to intimidate into silence any who push for that investigations by serving all exposing that election fraud to billion-dollar lawsuits. And that is certainly what has happened to Sidney Powell, Rudy Giuliani, and dozens of other lawyers and public officials nationwide who have pushed for that investigation. And Fox News, Newsmax and One America News.
There is a difference between Powell saying none of it is true (which she did not), and saying that the sampling of evidence she was able to find and make public warrants a much larger investigation (which she did) to fill in the gaps she could not fully investigate on her own. She is saying this for legal reasons, because Dominion, a multi-billion-dollar corporation is putting a gun to her head, trying to crush her with their unlimited cash for lawsuits against her. The same reason Fox News, Newsmax, and OAN are backing off. Not because they are wrong, but because Dominion can put a huge financial dent in them, regardless of right or wrong. The same way National Periodical Publications drove Fawcett out of business with their deeper pockets for litigation in 1953, and then once bankrupting Fawcett, DC began publishing Captain Marvel themselves. Not because they were right, but just because they could.