Those underground tunnels were built by the IDF. That's how they knew they were there, that's how they know their exact locations, that's how they had them mapped out already before attacking.
Hamas has built schools and hospitals another infrastructure.
Missiles and whatnot was funded by Iran, Turkey, Saudi Arabia, and.............. Israel - NETANYAHU'S Israel. He said so. Hamas is his al Qaeda. Just like Ronald Reagan had Al Qaeda created as a counter to the Soviets in Afghanistan, Netanyahu, Likud, and the Knesset backed Hamas as a counter to the PLO.