That is absolutely disgusting. There is zero reason anyone should need or be able to buy any more than one personal house per server. And SE really needs to put limits on that, soon. These guys are just an example, there are others that buy up property en masse like that to gain a monopoly on house sales, something that fills me with dread thinking about the second Shirogane opens up.
In their case I see it as less 'we want to live in quiet' and more 'look how much more money we have than you, lolol'. It's pretty clear to me they're only doing it to anger people, and they definitely succeeded.