From the LA Times article: "At one point the members broke into two groups, each standing around separate pianos to sing.". If you've ever watched a choir practice, this likely meant everyone facing inward toward the piano, and you can't stand too far apart because you need to hear everyone else to harmonize and adjust your volume. Singing loudly is probably only second to sneezing in terms of projecting atomized 'stuff' from the respiratory tract into the air. So there were 30 people standing in a circle spraying droplets directly at each other.
It may very well be that it's very easy to spread this virus, but I don't think this incident is a good indication of that. It seems more an indication of how poorly even well-intentioned people understood the contagiousness and what exactly social distancing meant at the time this happened (1 month ago).
I suspect that the risk increases the longer you're in an enclosed space with someone shedding the virus. Thought experiment, if spending two hours in the church with people singing meant 50% got infected. Then spending 5 minutes assuming it's linear (and it likely isn't), is only a 2% chance.
Brings up the difference between public health risk and personal risk. Public health perspective you want contacts to be infrequent and importantly short.
It may very well be that it's very easy to spread this virus, but I don't think this incident is a good indication of that. It seems more an indication of how poorly even well-intentioned people understood the contagiousness and what exactly social distancing meant at the time this happened (1 month ago).