More cloud magic
The OP raised a very good question when they spotted this mysterious cloud formation in the sky. Who in their right mind would go into the air and create smoke messages at that time? It’s already night, and the person who the smoke writing was intended for was probably already asleep!
As you might have already guessed, these smoke remnants aren’t from some poor sky writer who was forced to work during ungodly hours at night. Instead, these were produced by a rocket that was recently launched into orbit. The OP, who lives near a launch complex, really should’ve known what it was.