The man literally yells at Denjiro with open arms (usually something you do when going for a hug or going "ayeeee brrothaa whatsss goood?") and a giant smile on his face. Even laughs in a friendly way while conversing with him. They've talked with each other to an extent that Sasaki knows/thinks that Denjiro loved his Pompadour, while Kyoshiro knows Sasaki isn't the type to leave the party.
Even his reaction here is like "Yo wtf you doing bro?? What's the big idea here?"
Just based on their interaction you can tell the dudes know each other pretty well and are on good terms.
The fact that Denjiro asks Sasaki that whether he knows the History of Wano and Sasaki has a ?! tells us Sasaki is clueless about it.
So obviously Denjiro isn't gonna kill a guy he's on friendly terms with and possibly is good friends with.. who is oblivious to the history of Wano, when he went out of his way to completely restrain him.
Oda can either be saving Sasaki for post-Raid war, or having Sasaki turn good and joining the fight against the Beast Pirates later. But as far as this raid is concerned, Sasaki is out of the way now: