There could be several reasons why an admin might want to delete all Facebook group posts. Here are a few possible explanations:

1. Content Moderation: Deleting all group posts can be a way to enforce content moderation policies. If the admin identifies inappropriate, spammy, or offensive content within the group, deleting all posts can help ensure a clean slate and create a healthier environment for group members.

2. Group Rebranding: In some cases, an admin may want to rebrand or redefine the purpose of a Facebook group. Deleting all posts allows them to start fresh and reshape the group's focus or direction without any existing content influencing the new vision.

3. Privacy Concerns: If a group's privacy settings were compromised or the admin wants to protect the privacy of the members, deleting all posts can help remove any personal or sensitive information that might have been shared within the group.

4. Cleanup and Organization: Over time, a Facebook group may accumulate a large number of posts, making it challenging to navigate and find relevant information. Deleting all posts can help declutter the group and make it easier for members to find important discussions or announcements.

5. Transitioning Ownership: When transferring group ownership to a new admin, deleting all posts can be a way to respect the privacy of the previous discussions and allow the new admin to start fresh with their own content and guidelines.

It's important to note that the decision to delete all Facebook group posts ultimately depends on the admin's specific reasons and goals for the group. Communication and transparency with group members about the intention to delete posts can help manage expectations and maintain trust within the community.