Contributing in a big way to the short interest (according to Bloomberg[0]) is a single trade meant to hedge Soros $550m position purchased off of Ichan just before the IPO.
[0] https://www.bloomberg.com/opinion/articles/2019-05-07/lyft-s...
[0] https://www.bloomberg.com/opinion/articles/2019-05-07/lyft-s...
They might have edged their position by issuing an actual short, I'm only saying they don't necessarily have to.
From what I understand they make their money off of a deal like this by either taking a cut or fees.