You just deleted them from the surface, but they are still in your Twitter Archive!
Do you know what Twitter Archive is? Twitter (X) keeps a record of your tweets, followers, lists, and many other things in your Twitter Archive. You can always access and download your Twitter archive ⬇️ and see what you had in your Twitter past!
When you delete a tweet from Twitter, it still exists in your archive. So, you need to delete them from your Twitter Archive. There is a "tweets.js" file there. It has all your past tweets!
If you use Circleboom and delete your Twitter archive, you can delete tweets permanently, and they won't reappear!