This sort of thing is more common than most people realize - it just doesn't normally get public attention (the microscope that's being applied to the 737 presumably the reason this made headlines). Something fails more often than anticipated, or in an unanticipated manner, and the airframer realizes they need to do something about it.
Boeing recognized the issue and had already released a MOM (Multi Operator Message) recommending the actions in the AD. However the airframer does not have the power or the authority to mandate anything - that has to come from the Feds - usually in the form of an AD. It is rare that ADs don't reference an existing Service Bulletin or other airframer communication - in fact it's not particularly uncommon for the airframer to go to the Feds and request that they AD some action that the airframer has already recommended. Otherwise some operators simply won't do it.