Farmed animals like minks and racoon dogs were kept in cramped breeding conditions. Rhinopholous bats infected with sarbecoviruses are also present in Hubei. Those bats probably roosted above the animal pens and shit down on the animals below for years. The animals would periodically become infected. Eventually through mutation or recombination a strain became epidemic in the animals and evolved to be successful in a very closely related ACE2 receptor to humans.
Then you had a large bioreactor which spread the virus doing "gain of function". Eventually it swapped backwards and forward from humans to those animals until it acquired the ability to spread epidemically in humans in late 2019.
That process absolutely could have evolved a furin cleavage site, or it may have simply been present in the bat version of the virus (like the RacCS203 sample from Thai bats). Recombination with human HCoVs may have also happened in this process where the intermediate animal coronavirus infected a worker who also had a cold.
When you read last year about the Danish mink farms with millions of mink being infected with SARS-CoV-2 you should realize that is a much better bioreactor to do natural "gain of function" experiments in than any BSL lab in the world has. Something like that, with a similar species, is likely how the virus hopped from bats to humans.
This actually better explains all of the suspect features of SARS-CoV-2 than a BSL program does.
This is an alternative hypothesis which is simpler and less convoluted and does, in fact, completely undermine the "it can't be anything other than bioweapons research" argument.
You're aiming your criticism at the wrong end of the argument.