I'm afraid it's the "welcome back".
You do not lose your manager ranking when your account goes inactive. This is, presumably, to allow returning managers to apply for a club of their choosing, and not be pushed out by any other manager who applies, no matter how low rated they are.
As soon as you have your new club, your manager rating is reset back to (effectively) zero, because manager ratings are based on the last several seasons worth of results. Since you have 0 wins during that period, your rating will be 0. Therefore your manager ranking will drop to the very bottom again.
The good news is that the only way is up from here. Until you reach the end of the manager rating cycle (which I speculate is 5 seasons), your manager rating will only really improve, until you're back at your "actual" level.
