I missed the last one, but I clearly remember the two siyyumin before that, in MSG. The women were in the top box and could barely be seen. That is not comparable to the open air football stadium it is held in this time. So I can easily see why certain groups might avoid the event without a mechitza.
Who should decide if it makes good business sense? The group organizing the event. If they don’t think that they can fill the seats (100,000 this time – more than triple the capacity of MSG) without those groups, then it is prudent to make a mechitza to accommodate their patronage. If they do think they can sell out without them, but still decide that they prefer to have these groups attend over others who might not want a mechitza, then it is their choice. True, it may not be the best decision in profitability, but it is still a business decision just making handicapped seating available at sold out theatre shows.
In other words, mind your own business.