Your current website has accumulated search rankings, backlinks, campaign URLs, form destinations, consent rules, analytics events, and publishing habits. A new design does not carry those across automatically.
Traffic often drops when old URLs 404, canonicals point at the wrong page, or analytics and consent break on launch day. Before design starts, we record the current URLs and measurement setup. Most of the sites we relaunch are WordPress.
Pre-launch we test the redirect map, forms, consent, analytics, mobile performance, and inquiry pages. After go-live we monitor crawling, indexation, rankings, forms, and conversion data for six weeks. Your team sees what changed and which issues need correction.