Now that I have time to read up on the news, the briefness of CLH resignation is very telling. No letterhead, no title, signature also digital. Huge contrast compared to TCJ.
My guess is, yesterday Sunday, TCH must have called him to prep him. CLH kept in the dark.
Today morning 0800hrs, TCH submit his letter. LHL already prep his acceptance letter. TCH has until 1000hrs to clear out of his office, handover documents, ID pass, etc.
CLH was likely told she was sacked and had to "resign" at 1100hrs and submit her letter by 1200hrs.