Why did beethoven write moonlight sonata?

The Moonlight Sonata was not written by Beethoven for any specific reason or event. The title "Moonlight Sonata" was given to it long after its composition by the poet and music critic Ludwig Rellstab, who was inspired by the first movement's dreamy and emotional character. Beethoven originally titled the piece "Piano Sonata No. 14 in C♯ minor, Op. 27, No. 2".