I'll have to be honest. We've all been on aboard planes before, and we've probably been in situations where the plane had to land in rain or foggy conditions. I remember once when a lightning struck the plane that I was in on a journey to Hong Kong, the pilots still made an effort and got us landed safely at the airport. But in this incident, there's a president on board, most prominently the most important person of Poland. And yet, the accident was simply caused because of "pilot error"? That is pretty hard to believe, especially in the 21st century where disciplines are very broad and seriously considered. It's possible that there might be something behind the scenes (At the moment, no-one can tell what it can be).
But this is still a great assumption. I cannot formally propose such an idea until it is proven with solid evidence.