No, motive was simply revenge as it was with Litvinenko, Yushchenko et al. Recall that Yushchenko too, like Kaczynski, was pro-West. Also, getting rid of Kaczynski will certainly discourage his successor from keeping Poland in this missile defense deal, as it is well known how furious Putin was with it. So, to avoid Putin's fury and therefore similar fate as Kaczynski, successor to Polish presidency will likely think twice.
let us presume that you are able to convince us all here and all people of the world that Russia organized assassination of Polish president
Do you know what could be consequences for Russian-Polish relations?
Do you know what could be consequences for Russian relations with other Slavic countries?
Do you know what could be consequences for Russian relations with NATO?
Do you know what could be consequences for Russian relations with EU?
Do you know what could be consequences for Russian relations with USA?
Do you know what could be consequences for Russian relations with the rest of the world?
Can you image level of sufferings of complete Russian society, man, woman and children if you manage to convince people of the world that Russia organized assassination of Polish president?
Are you aware that your ideas (such ideas) lead Poland and complete NATO/EU in military conflict with Russia? Are you aware that, if you are right, Russia in fact attacked one NATO country and started war, possible even nuclear war? Because Russia was motivated by revenge on Kaczynski, by your words?!
Are you aware that after disaster of Polish presidential plane in Russia, now NATO and EU, if just want that (no matter real reason for disaster of plane) could easily found excuse to attack Russia?
Why would Russia create this situation? In this moment?
Can you comprehend what you talking about? What are you?