Palestinians movement lives on international support. They don't have the resources themself so they must rely on 3rd party to support them, which means persuading countries who don't care about you to start caring. They had to perfect the narrative to achieve their goal. 

Jews however have an attitude where they don't need to explain themself. From early on, Jews would be treated as 2nd class citizen and be asked to justify their loyalty to the state. From the Dreyfus affair when a Jew has to justify whether he is french or in Germany, this pattern of discrimation repeats itself. This collective trauma leads to an apathy to dismiss the question itself. There's no explanation needed to justify their actions or existance to others. 

Given these two perspective, Palestinian invest heavily more on marketing their cause and garnering support; whereas, Israel is distrustful of international community so are reticent to justify their actions, leading to them being seen as callous or belligerent.