Because of how filesystems work. There’s basically an index that tells the OS what files are stored where on the disk. The quickest way of deletion simply removes the entry in that table. The data is still there, though. So a data recovery program would read the entire disk and try to rebuild the file allocation table or whatever by detecting the beginning and ends of files. This worked better on mechanical drives than SSDs.
Right, like “hey I’m going to post insulting and repetitive tripe and empty slogans, and make Lemmy worse after lunch today!” Great. Also, as countless people have pointed out, if they care so passionately about Palestinians, their activities are contrary to helping Palestine so…