Plus as a hiring manager, and this is minor, I’d feel kinda embarrassed if out of sheer statistical luck multiple candidates turned down written offers, which would indicate maybe something is wrong with us as a hiring entity.
Not sure there’s a playbook here. Another commenter suggested being untruthful and pulling the offer out of them. Given how many times companies screw over employees that might be the game theory rational thing to do here even though it’s not great ethically.
Just my 2 cents.