Linux isn’t really a Unix clone. If Linux was a clone of Unix, it would be Unix. It isn’t, it is Unix-like. The word “clone” implies some small part of the original is cultivated into a new cell-for-cell replica of the original. Linux was created afresh, to have the look and feel of Unix, and to fulfill the same needs. It’s less a clone, and more a replicant.
But either way, Linux was a kernel looking for an operating system; GNU was an operating system looking for a kernel. In hindsight, what happened next seems inevitable. It also changed the world.