i think it’s likely they underestimated Israel’s ability to mount a response for multiple reasons.
from what I’ve read they expected Hezbollah at the least to join in, and possibly Iran and the Houthis too. There’s been evidence that Hezbollah had plans drawn up to invade the north in a similar fashion. A joint two prong invasion would have been crippling for Israel- the response was slow and fragmented as it was. Add in a northern invasion to the southern invasion on Oct 7th and the damage and chaos in Israel would have been incalculable- that would have certainly affected Israel’s ability to respond.
there was massive civil unrest in Israel before October 7th, I’m sure they were relying on a fractured and divided people being unable to work together.
The date was also psychologically and militarily significant- it was very close to the 50 year anniversary of the Yom Kippur war. Simchas Torah (the festival that Oct 7th was on) is part of the same group of festivals. they’d have also been aware that many soldiers would be home for the festival.
It was also led by Sinwar, himself released in a hostage exchange - he knew what price Israel would pay to get their people back, and likely calculated on being able to stop any Israeli response using the hostages.
there’s also a historical pattern of hostage taking by Hamas and massive prisoner releases in exchange- they may have been counting on that.
But ultimately, I don’t think that sinwar cared. He got his own wife out- what about protecting everyone else?!?even if he thought he could stop any response from Israel through hostage negotiations, wouldn’t you make a backup plan to protect your people?
@Twiglets1 netanyahu seems to be going hard for an all for all deal .https://www.timesofisrael.com/liveblog-august-12-2025/
There was a brief point at the end of July where it seemed negotiations were getting somewhere, the Arab league were pressurising Hamas, and then it all fell apart.