Landing 3 helicopters in a stadium may be safe in clear weather but in loose snow it is a different story.
It wasn't a stadium. An obstacle free gigantic field
in front of the stadium, big enough to give room for 100.000 visitors on concerts, large enough to land 30 helicopters simultaneously. Weather was not so bad, round about 2km visibility. A routine job for experienced pilots to land 3 ships with troops on such ground. Troop transport day and night is a main task of the Super Pumas and they have done it again and again, also on snowy conditions.