Despite the likely assassination of Mohammad Deif, Hamas leaders are still keen on a deal even without a permanent cease fire. Walla military correspondent Amid Bohbot says that the reason for this is the threat from both Qatar and Turkey to expel Hamas leaders if they don't do a deal.
According to Bohbot, what Hamas leaders care about most is their life of luxury in Qatar, which they do not want to give up. After looking at the alternatives to Qatar and Turkey such as Iraq, they realized they are stuck, and that if they want to keep living it up - they need to negotiate with Israel. Subsequently, they have been pressuring Sinwar to become more flexible with the mediators.
It should be noted that the main reason leading to Sinwar himself becoming flexible is the IDF's progress in cutting off the Gaza Strip from the outside world and applying heavy pressure everywhere else throughout the Strip. Right now, stopping the war trumps all else for him.