The Palestinians could prosper if they accepted any of the multiple offers for their own State. They would have endless support from the International community to ensure their prosperity.  

They've rejected every single offer.  They completely reject the idea of a Jewish State in present day Israel.  They deny 3,000 years of Jewish heritage and history in the Holy Land.  They deny that Jews have always been there.  

Until they accept that Israel is not going anywhere, they'll continue their misery.