With regard to your last question, everyone has an Apple ID and that ID works as an Apple email address; although you can use your Google account as an Apple ID. I don't even use my Apple email account, other than to destroy the junk messages that I get through it. But yes, I can see how other people might open an empty email and get hacked.
It's not just other people. Even the technologically adept could fall for this.
For example, you mentioned above that you only use it to destroy messages. But have you ever opened a junk message at any time to see what they were? That's all it would take for it to happen to you. If I used an iPad, it could happen to me, too. I'm not saying you were hacked. Just that it could happen to you if you opened any emails in your mail app. I'd assume that these special emails had an interesting subject line to entice people. Even us tech guys can't be complacent and think that stuff like this couldn't happen to us when a few quick taps and it presto, we just did.
I have to say if you can remember that the apple mail never crashed, I'm impressed. Not that it never crashed but that you'd remember it. I can barely remember what I did last week!

Although if it never crashed so a crash was really notable that'd be cool, too. I don't recall Gmail crashing but I won't go so far as to say it never crashed. But like I say, I don't have a great memory.