Because you've leapt from a comment about "understanding risk", to a statement about cause-and-effect. With a phenomonon like viral infection every risk is about probabilty; you can only blame people (and criticise them) if wearing the right PPE*
*A good-quality set of hindsight goggles
A 'risk' is about the likelihood of a an event happening, the event here being the passing on of a serious infection by a group of people who spend their entire working lives treating people with that very serious infection, and by last Christmas the risk of asymptomatic infection was extremely well known. As none of the clinicians had donned their PPE, but had sat apart from each other, the risk (or likelihood of an asymptomatic carrier among the group) was high.
So yes, this group of people who deal with the infection daily, took an unnecessary level of risk in holding an unnecessary meeting, in an unnecessary manner, putting others at risk through infection, cancelled operations, adding to the workload of fellow clinicians and costing thousands and thousands of pounds. Anyway, let's all focus on the Government and not blame my fellow NHS workers for cocking up shall we? Trust me, I could tell you some horror stories about PPE.
Oh, and I don't understand why in a viral infection the risk is about probability? ALL risk is about probability, if it wasn't then it wouldn't be risk, it would be certainty!