It's a shame because the design is actually quite clean - I can see the effort you've put into the layout and the copywriting. But if this site just lost all its impressions and got deindexed, I'd put my money on a technical issue rather than a content penalty.
Think of search engines like a nervous postman. If they show up and find a door that's locked, or a sign that says "no through road," they don't come back. That's exactly what happens with crawl budget and indexing signals.
First thing I'd check: did you accidentally add a noindex tag or block Googlebot in your robots.txt? That's the most common "overnight" culprit. I've seen it happen after a CMS update or when someone copies over a staging environment.
Second: look at your sitemap. If it's returning a 404 or a 500, Google stops fetching it, and new pages or changes won't be picked up. You can verify that in Search Console under Sitemaps.
Third, and this is a bit more subtle: check for a massive spike in 404s or soft 404s that might make Google think the site is broken. Sometimes a URL structure change - even a small one - can cause huge swaths of pages to return errors, and the algorithm responds by pulling traffic.
Also, if you've recently changed hosting or DNS, or if your SSL certificate expired for a day, that can spook the crawlers. They'll retry, but sometimes the "trust" takes a while to rebuild.
If you want to share your Search Console screenshot (anonymised) or post the site URL, people here can take a quick look. But start with those three checks - the fix is usually simpler than the panic suggests.
