Remember too that TMZ - specifically, the correspondents that work for TMZ - is also interested in what a celebrity does and where, unlike ABC, CNN, or Fox, which only cares about a celebrity if and when something that is otherwise newsworthy (for them) happens. So there may have been contact with TMZ, for other reasons, before there was even a crash. TMZ doesn't get beaver shots of Britney Spears getting into Mercedes if they aren't aware of a celebrity's schedule independent of catastrophic events. I don't know if it matters, but Harvey Levin also served in the California Air National Guard; there may be contacts there that play into this.
Speaking of, for all the critique of TMZ - warranted, I'm not going to try to defend them as I would Fox - Harvey Levin is a fascinating figure (I don't necessarily mean in a good way). He also is the legal expert for the People's Court (I met him once in that capacity), and had a (seemingly) short run where he interviewed some big name celebrities; the conceit was that he would focus on one object or item that meant something to the celebrity, and build a profile around it. He's an odd guy.