I live in a river valley that tornadoes generally jump over. I also live on a hill much higher than the river will ever flood even in a catastrophic event like this.
And yet, back in June...
No tornado, just high-speed wind. And a lot of our neighbors got it worse than us. Trees through people's windows, branches on cars, some of the roads in our subdivision were completely blocked for a couple of days. Houses are still being repaired.
Trees usually grow more wind resistant if they are exposed to more wind. This might just mean that your climate is also changing (quickly) or a unusually strong gust of wind came along.
The particular tree also might have been sick.
Had one of those in my area a few years ago. Just like 5 minutes (probably less) of a freak strong wind and the massive tree in my backyard fell, along with many others. I've never seen anything like it before. Well, I probably have, just at an intensity low enough that it was a non-event.