1, the meaning of sending a congratulatory message is a bit ridiculous, that is, teasing and laughing at others. It means that something very tragic happened to someone, and then someone watched the joke and used the word "send a congratulatory message" to celebrate schadenfreude. For example, people who eat melons send congratulatory messages.
The original intention of sending a congratulatory message is to congratulate the person who received the telegram.