I would have done the same except maybe leave the snake where it was.

Doesn’t really matter what did it but a nest that easy to see it could have just as easily been a jay or grackle responsible.

Anyhoo... the mockingbirds will just start over in another location around the yard and try again, if songbirds couldn’t do that they would have all gone extinct a long time ago.

"...if the gentlemen of Virginia shall send us a dozen of their sons, we would take great care in their education, instruct them in all we know, and make men of them." Canasatego 1744