I have at least 7 emails I use at any given time. I use my Apple email strictly for Apple and literally dozens of Apple devices I own or support, I think I get one or two spams a year, and it's always from the same spammer.
My work email, which I only use for work is about 50/50 legit and spam, and this is with a hardware spam filter enabled.
My google email which I use for everything else (I maintain 5 of them) sorta bad, manageable, my Microsoft accounts (I have 3, I used to have 6) the hotmail accounts are inundated with spam; the previous ones I had to abandon.
If you used your address on a forum, website, questionnaire, email, an online sale, a food truck or basically any system anywhere on the world... These are some of many ways for a spammer to get info