Sasaki was a former pirate captain that was most likely defeated by kaido or the one of the calamities and then was asked to join or die, so there chance Sasaki wasn't part of kaidos crew when they took over or when oden died,
Kyoshiro caring about whether Sasaki was forced to join or not (THIS IS UNCONFIRMED) doesn't matter unless kyoshiro has very clear reason to believe that Sasaki will not go on a murder rampage if the alliance once gets freed. Like for some reason Sasaki who was all in with rising in the beast pirates ranks will change sides because Denjiro told him some sob story.
Unless the above happens and Kyoshiro knows it will happen yet we the readers have not been shown that Sasaki gives a shit, then Kyoshiro is fuckin stupid