Because he’s a coward that can easily hide because his fruit makes him so malleable?
And you think a machine that Luffy was abl to figure out is complicated?
Luffy was told what they do… The machines are tech no one has heard of, it’s you don’t just randomly look at them and say “this is a good making machine”
Also there’s the question of motivation
the biggest reason it’s Kizaru is that we know he’s motivations very clearly
he wants to save his friends but he also doesn’t want to lose his job… those two things are enough motivation both for him to do this and for him to be sneaky while doing it
Why is caribou helping Luffy here exactly? Let’s not forget that Carinou helping in Wano only occurred because Caribous literally had a direct deal with Luffy to get him out… for caribou to help Luffy here you would have make up a motivation like he believes the strawhats would just like him enough to invite him on their ship or something (even though they didn’t see him help Luffy to begin with)
And of course with lafitte it’s entirely headcanon what his motivations would even be here