There's circumstantial evidence.
1. The Wuhan lab was French built and supposed to jointly operated between France and China, but the French sounded the alarm about the terrible security practices of their Chinese counterparts.
2. Ecohealth, an organization with ties to the Wuhan lab, did a grant proposal to DARPA asking for money to do gain-of-function research on COVID. To be clear, gain of function research usually is something along the lines of: let's make this pathogen able to infect humans so we can study how it might infect humans if it ever evolved the ability to infect them.
3. It's dangerous research and should only be undertaken carefully, rather than in the haphazard way in which the French claimed the Chinese were engaging in research.
4. People close to the situation categorically denied that a lab leak was even possible, calling it a "conspiracy theory" although they knew that the lab had been doing similar research on similar diseases, and had declared an interest in doing so with COVID.
It's like if there was an organization that declared they wanted to make unicorns real, and they had made other fairy tale animals real in the past, and then unicorns appear in the wild in the same city where this organization is based, and they're like, "It is a conspiracy theory to think we had anything to do with this."