[since] what you say is true,
(1) Why hasn't Israel used it's intelligence to search out and destroy Al Qassam in Iran?
FTFY. Thank you! Sadly, the answer to that question is that the Likud party benefits from an Arab genocide. Check the polling. Israelis are caught up in the same hysteria, and they LIKE it when Arabs die. I hate to put it that way, but Netanyahu knows this, and sprung his party's 2nd Nakba plan into action amidst the confusion surrounding Iran's attack on Israel. Netanyahu knew that Team Israel would applaud just the Israelis would, at the ITF massacring Arabs; all they had to do was to peridocally announce "We bagged a Hamas leader" and Americans would be high-fiving each other.
Gazans did not attack Israel. Nonetheless, their genocide has spiked Netanyahu's popularity by a wide margin and caused the Likud party to pick up seats in the Knesset, making them the largest representative party. None of the tens of thousands of people massacred by the ITF ever attacked Israel or had anyone hiding behind them. This is just Israel mad with power and hell-bent on ridding themselves of their Arab problem once and for all.
Oh, Israel didn't want to pass up the opportunity to smoke the Arabs just to exact retribution on Iran. They have their priorities, and now you know what those priorities are.
They should be able to pinpoint their whereabouts, and the hostages, couldn't they?
Nope. Once Al Qassam absconded with the hostages and returned to, most likely, Qatar (where the hostage talks were held), there was no chance that the ITF was going to somehow find them in Gaza. When Trump warned Hamas (who did not attack Israel and who did not have any hostages) to return the hostages or else he would rain down holy hell, there was no chance that his warning could bear any fruit, which is why it didn't. Nor did Trump's second warning nor his third. Have you noticed that Trump hasn't rained down holy hell on Hamas? Trump always follows through on his threats/promises. What happened? Well, Hamas were nothing more than Gaza's public administrators, and they have no money and no military. They grew out of a charitable organization (like the Red Cross) and became a political party to run Gaza. They are now all dead. Feel free to speak about Hamas in the past tense. Hey, Team Israel applauded and cheered their deaths. Nothing has been done to Al Qassam, the perpetrators of the Oct-7 attack on Israel. They're all laughing at Team Israel for cheering and applauding the slaughter of a group of people who never attacked anyone.
(2) And how would Hamas have gained control of the hostages that were released?
They didn't. Hamas are all dead now. The negotiations, when they occur, are with Al Qassam's representatives in Qatar. There is no Hamas in that equation. They're all dead. Certainly you remember all the cheering and applauding and high-fiving. Gaza has no public administrators left, but that's OK because there's no Gaza remaining either, so they are no longer needed.
Weren't a few hostages found dead and lots of munitions found in the tunnels in Gaza?
I believe there were a handful, and I'm not sure what happened with them. The main body of hostages was removed from Gaza, and the ITF knew this, which is why they indiscriminantly air-striked buildings they were claiming they were searching for hostages, but really weren't.