For reference: almost all deletion on Stack Overflow is "soft", and deleted Q&A can be viewed by users with at least 10,000 reputation. These users can vote for undeletion, and the author can edit and submit for undeletion.
It looks like the answer you're talking about is now undeleted, with yours among the three necessary votes. (It also looks like you accepted, and awarded a bounty to, a different answer back when you asked, and the answer you're now calling "best" was posted months later. So it goes.)
The explanation for the original deletion is exactly as ayhanfuat says. LLM and other GenAI content is forbidden on Stack Overflow (https://meta.stackoverflow.com/questions/421831/), since before that answer was posted, and the author (one of the site's most prolific contributors) got in trouble for a flood of such answers. (It took quite a while for the problem to be noticed and acted upon, in large part because of a moderation strike in June 2023 which ended up creating a large backlog of flags for AI content, and in part because custom flags are required to report this. The strike, in turn, was largely about the company/staff trying to interfere with moderators attempting to detect AI content, with the site owners being unwilling to accept false positives because it would be "unfriendly". So it goes.)