But before computers it was just called Mathematics. Computers are really essential for the existence of Computer Science.

Before electronic computing machines pretty much took over, "computer" was a job title/description. The exciting part of Turing's On computable numbers, with an application to the Entscheidungsproblem was his abstraction of what computers actually do to a simple machine. Large chunks of what's currently being explored is in relation to problems that we may or may not be able to solve using machines we're not even sure can, in principle, be built, and on that level "computer science" assumes spherical cows in a frictionless vacuum. It's nice that we have relatively compact, fast and nearly ubiquitous machines with which to apply some of what's been discovered along the way, but fundamentally "computer science" is the mathematics of process.