That Hamas was open extremely early on in the conflict to negotiations for returning hostages and Israel and the US knew this while they waged a bombing campaign and pretended like Hamas wasn't trying or willing to return hostages.
Negotiations weren't happening because Israel didn't want those negotiations, not because they weren't available.
And, I don't know if you are aware, but negotiations involve give and take. Israel didn't need to "traded for all of the concessions Hamas wanted in exchange for them".
The reason the hostages weren't returned sooner is because Israel didn't want them. In 2024 Hamas accepted all of Israel's terms multiple times only for Israel to change terms. Israel knew they'd have fewer justifications for their genocide if they got the hostages back.
That's my point.