In my opinion, the simplest explanation of this is: a worker at the Wuhan facility was accidentally infected (mistakes happen) and it was able to spread. It was not intentional.
An intentional leak would be an attack. I don’t recall that being on the table during the early part of the pandemic. I’m sure there was a least one person suggesting it but I recall the lab leak theory being the most ridiculed was some kind of accident or mistake at the lab resulting in an infected worker. …probably asymptomatic to boot.