What collateral damage is being done? It seems to me the opposite of collateral damage is being done: Mailchimp has banned cryptocurrency-related email lists, and those writing cryptocurrency-related emails have lost that ability.
Beyond the absurdity of the title, email has always been decentralized. Anyone with a server can send or receive email with whatever technology stack they so wish. Of course, because there is no trust framework, there's no guarantee that your email will get delivered… Which is why Mailchimp validated the opposite of the article's conclusion: there is lots of value in centralizing the management of email. They can act as a trusted authority to negotiate with various email hosts and guarantee(-ish) to customers that the emails will get delivered.