Pattern
You may be joking but in the last week I've had two phishing e-mails, the first to an address only ever used for Swiftcover motor insurance (of whom I stopped being a customer two years ago) and the second to an address only ever used to register/unlock freebie software from Ashampoo (and from whose mailing list I unsubscribed late last year).
If I were writing a novel, I might envision a scenario in which spammers with deep pockets approached individuals within companies and offered them substantial remuneration in exchange for lists of e-mail addresses. Especially those that belonged, for instance, to former customers who no longer represented a value to those companies.
But then I'm not writing a novel, and things like that never happen in the real world do they?