To the people who say its crazy to have them all on the same flight it isn't that unheard of. In America we sometimes times have the President, Sec. of State plus various congressmen on the same Air Force One flight.
Including the highest ranking members of the military and the chairman of the Fed?
... I don't think so.
I don't really see a reason to be suspicious of any government. They were obviously all important in being at this particular type of memorial and it may have saved more time by cramming as many people as possible onto one plane.
The reason for the crash seems to have been pilot error/technical failure. The airport did not have ILS which is needed to properly guide a plane through the heavy fog so they recommended that the plane go to another airport. Another Russian pilot with a lot more experience at that airport had actually tried twice to land at that field and gave up but the Polish pilot crashed on his fourth attempt.
But it's actually likely that the politicians on board were pressuring him to try to land there. That pilot had shown some spine in another similar situation by flying to another airport despite the president ordering him to land under poor conditions and apparently he got an earful for it. The president was apparently notorious for trying to meddle with the pilots' jobs during government flights.