Do you mean these rich owners should support their employers a lifetime or while shutdown? What if the lockdown lasted for about a year? They aren't obliged to do it since in the first place all are affected. Being them as rich doesn't play a role here. It's nice though if they will do that.
As long as the company supports them during the early weeks, that's fine. The salary and additional bonus should be well enough to cover at least a month. But if no support made then that's the time they can shout to the company and even sue them.
The government itself must play a role here to provide assistance to all, not the owners themselves. And I know these companies and sectors are also contributing to donations.
Not a lifetime of course. At least maybe couple of months so as to keep them afloat for the moment while waiting for other's assistance like from the government. They should look into the real conditions of their employees. Not only in casinos but same with other businesses as well. They are also losing, but their employees are more vulnerable as they will have nowhere to turn to just to buy food on their table. I know someone here in my country, he has a resto business but what he did, whatever was left (stocks) in his resto, cooked it all and gave to all those that really needed it. And bought groceries for his employees during lockdown. I know this kind of person is rare, but considering that he is not really rich made me think that even in his own ways, he finds ways to help and that is if you really want to.