I’ve received emails saying my Apple ID willbe locked/is locked

Presumably you use that same email address for actual emails and for signing in to other web sites. So if one of the people you email is a windows user and gets hacked, the hacker gets their address book with your email in it so they can spam everyone in that address book. Or a web site you’ve used it for gets hacked and the emails stolen. There are literally dozens of ways a hacker or spammer gets hold of email address and then they just mass email every single one.

Spammers collect lists of literally millions of email addresses gathered by one means or another from hacked personal computers, hacked web sites, robot web scrapes from public places where people post their email address (one of the reasons never to post an email address here), and they barter and sell them to other spammers. Once your email address is known to one spammer, it quickly is known to many. And then they just spew out their scam/spam messages by the millions to every address they grabbed up.