The reason is no one expected then to be dead after that shitshow he did with Kinemon, even moreso with Izo, he just reunited with Kiku after 20 years no way Oda kills him.
This is the power of repeating fakeouts so many times, people stop caring about actual deaths because they think they are alive. Everyone coped for Monet to be alive and return in Dressrosa for whatever bs reason.