West bank and gaza in general are very different places with "different" population. I did hear in past sentiments from palestinians on west bank that gazans are uneducated animals. This can partly be attributed to what I wrote before: Jordan annexed west bank and kinda tried "uplift" population while Egypt let gaza rot for 20 years.
Israel couldn't handle hamas in gaza and this is why it pulled out. Just like it pulled out of south lebanon that had "sympathetic" south lebanon army.
After pulling out of gaza israel tried to keep control of gaza<>egypt border in order to prevent smuggling via tunnels but it wasn't sustainable without creating depopulated strip a couple of miles deep. there were considered "light versions" of it, but supreme court prohibited doing so and army realized that it pointless anyway. so israel pulled out of this area as well.
when israel pulled out there was expression "gaza can become either singapore or mogadishu, and it's up to gazans to decide". after israel pulled out all the agricaltural equipment that was left behind (also was controversial but there were hope that it will help to develop industry/economy) was trashed, houses were looted and hamas proceeded with shooting even more rockets and mortars.