The Palestinians are stateless, and the territory on which they live has no prior sovereign. Ergo, that territory is theirs to claim, and they have claimed it. Compare and contrast: the Kurds are not stateless: they are Turkish, or Iraqi, or Syrian, etc. The territory they want for their own state ALREADY has a sovereign: Turkey, Iraq, Syria. etc.
Hamas says Egyptian mediation has restored calm along Israel, Gaza border (Haaretz)
from the article: Why Palestinians yes, Kurds no?