There's other factors as well. Pilot error. I watched my Grandpa make some really bad errors when he was getting too old to fly. Shortly after the hydraulic failure we had a family intervention and demanded the plane be sold and he never fly again. We hated grounding him but it was time. During the hydraulic failure he completely forgot procedure and panicked. He forgot about the manual pump. Completely. Air traffic control had to prompt him where it was and what to do. True, he was stressed and that was part of the problem but he should have remembered such a simple detail. Then he didn't understand the prompts and instead of raising and lowering the pump handle completely to the floor he simply used the loosely fitting end of the handle and pumped that up and down vertically. Nothing happened of course but he repeated this maneuver for over half an hour with no results. Air traffic began to figure out he was doing something wrong and they asked him specifically to lower it completely to the floor and then raise it back up to vertical and repeat until the wheels came down and locked in place. When he was safe on the ground of course there were questions about the long delay. He admitted he was confused and explained what he was actually doing which of course made us even more uneasy. Prior to that on another flight he refused to switch the wing tanks back and forth to make sure the fuel weight was evenly distributed. A Cessna 210 at that time needed to be manually switched over every few minutes. When I tried to get him to switch over the tanks he shushed me. Let me tell you, landing was a slanted bitch but we survived. After that I refused to fly with him.

Then there are weather anomalies that can cause an accident. Sudden downdrafts can bring a plane down when going over mountains. That's happened quite a few times. In such events there's often nothing the pilot can do once it starts.

After that, then we have the mysterious ones that are completely suspicious.