I think that it is at least somewhat likely that it was the result of the lab's activities, but your assertion here has a huge dose of selection bias.
If the virology labs studying coronaviruses were placed randomly around the world, you'd be correct - but they're not. They're placed near locations where novel coronaviruses have crossed the species barrier in the past, and where they are likely to do so in the future.
It would be equivalent to say that lighthouses cause ships to run aground, because many teams when ships run aground it's near a lighthouse.