IMO: Things happen because they are intentional or unintentional consequences of people's actions; because of a coincidence of related or unrelated events; because of a natural or man-made disaster; because of a simple accident; because of a combination of both an intentional or unintentional event and an accident; because of biology, sheer fluke - etc., etc.
There's no "reason" - as in "higher purpose" - as to why one person gets cancer while another smokes all their life and remains healthy; why one person has unexplained infertility and another gets pregnant the first month of trying; why someone dies in a plane crash, another wins the lottery, another's house burns down; why one person meets their life partner at 18 and another remains single all their life. Even if someone has a sliding-doors-style "near miss" (i.e. not getting on the plane that then crashes), the reason is simply that they missed their flight, or changed their mind, not because it was preordained that they wouldn't be on that flight. Even if you believe in God, surely you can't think that he's looking out for the lucky person who somehow ended up not getting on the flight, and to hell (or heaven, I suppose) with the other 200 unfortunate buggers who did?
Things happen because of a reason, yes, but not for one.
As you can probably tell, I'm not a big fan of the phrase, 'Everything happens for a reason'... 