Some reasons:
The Palestinian conflict has been in the public discourse for a long time. More than a hundred years. Uyghur issues are relatively recent.
The Uyghur conflict is mostly a purely internal issue of China. The Palestinian conflict has been part of international politics, including an important part of the Cold War, since the creation of Israel and mainly since the Suez Crisis. Nobody expects the Uyghur conflict to be the spark to World War III. Many people feared that Middle East would be. In fact, nowadays many people are afraid of the current situation leading to a regional war.
The above points mean that a lot more people knows about the Palestinian conflict than about the Uyghur's conflict. And positions are more entrenched.
There is a larger Palestinian diaspora.
Palestinian conflict can be seen as an offshot of colonialism (people from Western countries going to somewhere else to tell the locals that they have no rights to their own land, because the Western people had good reasons). Call it "ancestral home" or "white man's burden".
As stated in the other answer, the Uyghur conflict is an attempt to absorb a population. The Palestinian conflict is an attempt to remove a population from their land.