I think this is the last time (or they could be more) we have seen such dust attack or simply promotion of a company, Spamming 547 satoshis. But why?

You're not alone, many forum users, especially those with high-rank accounts, have received dust to the addresses that they have mentioned in one way or another on this forum: https://bt.irlbtc.com/view/5175238.60

I received dust to an address that is part of a wallet that I stopped using a long time ago, so I'm not going to bother to burn it. Who knows, maybe in decades those satoshis will be worth hundreds of dollars, so with a bit of anonymization it could be spent safely?