If Hindenburg weren't financially incentivized to uncover this fraud, it seems likely they would not have bothered and many more people would get scammed by Nikola.
Journalists got to Theranos first, and short sellers got to Nikola first. With both in play, the odds of a timely exposé go up.
I knew several people who said what they were claiming was impossible but they didn't really have any interest in being the whistleblower.