Covid is skiing at every major resort, just like it's shopping at your grocery store, but because of the precautions in place, it's not likely to spread in either setting. This could've happened at any business.
At the first Buffalo Bills playoff game, they tested everyone who wanted to attend and about 2% tested positive. That means about 1 in 50 had it at the time. If there are 1000 skiers at a resort on a given day, then about 20 would statistically have it. Every business would be closed if they were required to close because someone there tested positive.
I believe they overreacted by closing. They were not required to or even asked to. This was a guest, not an employee. If an employee tests positive, it's a much bigger problem because they could've exposed other employees who now have to quarantine. If enough are taken out, it could close a resort temporarily, as happened at Hunter at the beginning of the month.