"Israel controls Gaza's water and electricity", "Israel controls Gaza's airspace and territorial waters" are the narratives we hear all the time, so you didn't provide anything new here. Still, most of us are left to wonder: How was Hamas able to build that huge network of 300 miles of underground tunnels, when they couldn't import materials to build one single desalination plant, "due to Israel's blockade"? In January 2017, UNICEF and partners completed the construction of a €10 million seawater desalination plant funded by the European Union, so that blockade was not really a blockade, correct?

Gaza only gets 10% of its water from Israel. The rest is from desalination plants. Hamas stole a lot of of the infrastructure pipes to build weapons, so a lot of places in Gaza no longer have running water.

Gaza was also given aid to build its own electrical infrastructure over the last 17+ years via UNRWA but the equipment was stolen and diverted to weapons. So they are still dependent on Egyptian and Israeli electrical transfers. They stopped paying their bills in 2017 so Egypt cut them off and Israel kept providing it for free (what other country in the world provides free services to people who want to genocide them?)

Most of the money came from EU donors, especially Germany, which is why many of the more Israel-friendly governments in the EU are suspending or reviewing their aid programs, since it has been obvious for decades that UNRWA promotes militancy and hatred of Israel and is really not a relief organization. It's a permanent aspect of militant Palestinian maximalist ambitions to conquer Israel.

Many of the things you say are correct, but you also have a blind spot when it comes to Palestine. Gaza has its own desalination plants (most of Israel's water comes from desalination also), and a pipe to Egypt as well, so it could provide its own water. But why, if the gas can go to rockets instead?