You have irrevocably licensed your content to Stack Exchange
From the terms of service section 3, as quoted in this answer:
You agree that all Subscriber Content that You contribute to the Network is perpetually and irrevocably licensed to Stack Exchange under the Creative Commons Attribution Share Alike license. You grant Stack Exchange the perpetual and irrevocable right and license to use, copy, cache, publish, display, distribute, modify, create derivative works and store such Subscriber Content
That is, you do not have the right to simply delete all of the content you have licensed, as it is no longer your right to do so.
Moderators are empowered to undelete and delete answers as may be appropriate from time to time. This may include instances where you have submitted valuable content to the community.
If you wish not to be associated with that post, you may use the contact link at the bottom of each page and request that - your username will be removed from the post.
If you choose to delete the post(s) again, moderators may choose to place a content dispute lock on your answer, and direct you to voice your concerns on meta.
You may be suspended for disruptive behaviour - there is no exhaustive list of reasons.
Also, if these are the answers and the situation I think it is, those are great answers and I would likely have made the same decision - although there is no magical "cutoff" after which posts will not be undeleted.