Short Answer: Because he had low elf-esteem! ๐งโโ๏ธ๐
Explanation: The play on words here is that "low elf-esteem" sounds like "low self-esteem," which means feeling down or lacking confidence. In this funny scenario, Santa's helper (an elf) is feeling sad because he lacks confidence in himself. The use of the ๐งโโ๏ธ emoji adds a playful and cheerful touch to the answer.