Usually when moving a protected page, the protection is transferred so it will retain the same protection settings as the old title.

Recently this has not always happened, and the page has lost all of its protection.

Related discussion at https://en.wikipedia.org/wiki/Wikipedia:Village_pump_(technical)/Archive_142#Protection_did_not_transfer_when_page_was_moved and https://en.wikipedia.org/wiki/Category_talk:Wikipedia_pages_with_incorrect_protection_templates#Page_moves.

This happened to me again today so it is still a current issue.