Some people have voiced concerns on less hits after upgrading. Some say less that half. For me with my board that targets a very small group it actually increased.
My 2cents:
It could be due to the URL's changed after upgrading to Threads. So it could take quite a bit of time to catch back up. Unless you desire to start re-submitting, sitemaps and url's to the search engines. And whatever other SEO method you wish to use.
