It's not likely that Gmail or your account have been hacked. I've always suspected that there is some 'overlap' of information in Google's own mail search database that others are able to access, somehow.

I use Gmail for only one thing, subscriptions. Yet I get mountains of spam, offers to extend my life or my dick, all the Nigerian plots, etcetera, etcetera. There are most likely some holes in Gmail that Google has not bothered or care to locate or fix. As long as their spam filter works, I guess you take it or leave it.

Liquor store employees, among a raft of others, are swiping their own air miles cards when customers don't present one. What's to stop a Gmail employee from selling a little information on the side. Can ALL Google employees be trusted? Doubtful.