Why too simplistic:

Palestine got invaded, ethnically cleaned and massively murdered for decades.

Ukraine was cultural a divided country where West and Russia alike used one band or the other to rein power on the entire country. However in 2014 the West overstep the pro-West, pro-Russia alternation with a Coup. Immediately 1/3 of the country got itself completely disfranchised (no vote, no representation, no even could speak its language) and a civil war ensured and then even that 1/3 got without no pensions or services. The sad thing is that the coup was not even needed since Viktor Yanukovych was going to be voted out in just 11 months, but Washington was not having it and needed its coup to put the alternation to an end and be able to make its long-wished constitutional changes to Ukraine . The rest is history.

Russia is not saint here, not at all, but Russia did get invaded and massacred multiple times by the West and every single time through Ukraine... I think if Moscow have a bit if concern it is perfectly warranted. Ukraine should have done what Finland did in 1940s-2010s, side with the West but full warranties to Russia of being fully Neutral and away from NATO.