cashash part of it may be overreaction (political) but there is also the issue that more than half of the grounded Maxs never entered airline service and may not have C of As. The continuing airworthiness requirements, in terms of safety assessments, are different for a newly built aircraft and an inservice aircraft - you can take time to fix an inservice issue (or never fix it at all, if deemed safe to take that route) but you have to fix many more such issues at CofA. (Both from a regulatory point of view and a commercial one - new customers don't like accepting aircraft with potential ADs etc hanging over them)