looking for correlation with any google change must always be the last thing to check for. if you look for correlation, you will always find some. there was an domain change and URL change with subideal old2new migration.
@OP, if there were in fact high traffic pages that got renamed, do a CSV/Excel export in GA/GSC/sitemap/etc., and map the old URLs to their new and implement 301's and wait and see if traffic starts to return.