I’m pretty sure, you’re talking about Ahrefs?
Cool down! Since Ahrefs has different crawl algorithm. And it differs a lot by GSC. So, it doesn’t mean the same quantity is going to be same as well in the Links to your Site section.
For the ranking drop, it’s obvious because the link you made on the blog might be having a completely different niche.
What can you do now?
I guess you’d already disavowed the link. I would suggest you, disavow the complete domain. Or if you know the site admin mail them to remove the comment.
And for the future, don’t just follow the crowd without having the actual strategy. Those spam blog commenting works pretty awesome just a year back and give a nice push to the serp’s. I too know some of the sites are still ranking with same comments. Ignore them completely.
Who knows future!