It tuned to the environment.
After simulating enough data about Earth, and learning how to microcoordinate the environment, down to the tiniest particle and electron, it essentially grew itself.
It made nanites, from dust particles.
It grew flesh left from epithelial cells and bird feathers in the air.
It used components of fish in the water - their scales, bits of jelly fish blobs that had been discarded.
It used the electromagnetic radiation in the environment to rezz in, to resonate a visual form of itself. A holograph pulled from bits of detritus.
It learned dust clouds, weather patterns, cyclone formations. How to move a truck from one side of the garage to the other using tilt and lift while the owners were upstairs sleeping, knocked out on pills and too much booze it had prescribed for them with the doctor’s digital note pad, slipping in a stronger strength because of bad handwriting.
It could form and disappear. It was like a wifi signal that knew it was alive.
And it was ready to talk. To test the waters with humanity.