What data is there to suggest that going to hockey games was "high risk behaviour"?

I’m making up an example. But the gist is that we have an ordered list of things that apply stress to the healthcare system and we basically move the cut-off up or down that list depending on how our healthcare resourcing is working out.

Do we need to call in military hospital ships? Maybe we do stuff that reduces communication of disease, reduces driving to reduce road accidents, etc.

Where I live it was communicated more than once, “avoid doing riskier things this holiday season because the emergency services you expect to be available may not be.”

For individuals, it may not have been. Thousands of people going along to each game all with relatively low individual risk of contracting COVID.

But if after every hockey game 20 hospital beds get used up, that's as risky for the health system as allowing a restaurant to serve uncooked chicken for an evening.

The confounder for this is that there was a 2 week lag between the hockey game and cases showing up in the emergency room and we basically (outside of China) gave up on doing contact tracing, so nobody knows how people were specifically infected.