For the same reason Dominion sued Fox News for having hosts and guests spread the lie about voter machine tampering, and not suing the individuals, hosts or guest panellists themselves. And they won $787m by the way.
1. Jaguar Wright doesn't have any money. She's close to homeless.
2. A crazy person has the right to be a crazy person and lie, but a multi-million dollar platform does not have the right to platform and spread those lies.
3. The only option after that is to go after her with a cease and desist or a gag order, and understanding how the culture works, ordering somebody to stop lying about you is equivalent to saying that she's telling the truth in the eyes of loons who believe her. Either that or be the billionaires suing a destitute schizophrenic and have the people who already don't like you have a tangible reason to continue not liking you.
4. Engaging with her in any way, legal or not, is giving her the oxygen to continue talking. She's unstable. She'd just take the lawsuit as a sign that they're engaging with her.
So it's best to attack the lies, and attack a platform, and not attack the liar.
Unless that liar has something you can take from them as punishment. Which she doesn't