80% loss in search visibility following 301 domain move

Hi,

On the 12th Feb, we moved from one domain to another. However, we have lost 80-90% of the search visibility, and it doesn't seem like it's improving. Here is some info.

1. 301s put in place via .htaccess for www and non www
2. Hosting provider for old domain created a redirect rule for every occurrence (either www or non www) so the .htaccess wouldn't have 2000 lines of code
3. Page for page mapping, and keeping URLs largely the same
4. Content differs between the old domain and new domain, but the keywords and content align
5. Put a request in Google Search Console to move the site, which was accepted
6. Submitted new sitemap to Google for new domain

NOTE: A developer had only a couple of months before accidentally changed the old domain from www to non www

The only thing we haven't done is reach out to companies who linked to our old domain to ask them to update their link.

Any help much appreciated.