A few days ago, I was looking through submissions from round 1062 (div. 4) to check for cheaters. I had the random idea to search for submissions made to a problem after AC. Surprisingly, several people got AC on a problem, and then submitted completely different code later (such as kundan_kumar_v and venkatsatish03). There were also some users who got AC and then submitted wrong solutions for some reason. The most interesting was Mr_prince_sahu, who spent 30 minutes programming 3 different solutions to A in 3 different languages. All of this made me wonder why would anyone do this?

Now, I have submitted after AC before (in round 1011), but that was for preparing to solve F2. In round 1062 though, there were no multi-part questions. Maybe they were maybe trying to fix some bug and avoid FST, but that doesn't justify reimplementing one's solution in another language (and then not change any logic, which).

EDIT: I got my answer

Note: all of this evidence was obtained by searching only 10k submissions from a single contest. There might be thousands of other cases of this, but I can't check because "Recently, your account was used to crawl. Please change your password to prevent your account from being used for unauthorized activities."