I am truly sorry that all that work has disappeared and understand the shock you must have felt when that happened.
Such a result actually is a foreseeable consequence of any large-scale,unilateral action taken on an SE site. These sites are community run. That does not mean that individuals do as they will and then ask that others accept the consequences. It means that members work together, collaborate, talk, test things out, and move forward with consensus. Meta and chat are two of the (many) mechanisms to support these activities.
I instigated the response to your actions after (a) rejecting two requests from you for a wiki edit on your new "analytical-derivation" tag (the description was vague and incomplete) and (b) receiving a strong complaint from a highly respected member of the community about the wholesale retagging. Those actions included:
Writing to the other stats mods about the retag-fest. (It was very early a.m. their time so no immediate response was expected.)
Consulting with mods on other sites and SE representatives via chat.
In response to their (unequivocal) advice, contacting the SE team by e-mail.
In the email to the team I gave the facts: we had an active, valued user who created a new tag and systematically retagged questions until he was notified of the "taxonomist" badge, then stopped. I then shared my own impression:
Sounds like abuse to me, although fairly harmless to the site. The tag would be potentially useful but IMHO has now been applied so indiscriminately that it's pretty worthless now.
Ideally I would like to have most of this tagging reversed but that could alienate this guy, who's pretty active. I'm also wondering how to head off such abuse in the future.
Finally, I did not specifically request any action:
I look forward to any suggestions you might have to offer.
I did not want to make a unilateral decision because that would be unfair to you and the community. I did not write to you because I felt that was premature: I was still seeking advice and guidance.
The moderators cannot (easily) remove a tag: I believe that was done by the SE team. It is an outcome I thought was likely when I wrote them, so I take responsibility for it. The message you received (from another mod) was a courtesy to let you know what had happened, why, and what to do in the future. If now, knowing more of the history, you have constructive suggestions for how I could deal with similar situations in the future, please let me know: I needed help with this one and welcome help from anyone at any time.
I think I can speak for many in saying we value your interest in and engagement with this site. That's not just empty words: in my opinion, the quality of your answers is increasing and they have become regular and welcome contributions. However, as a relative newcomer, your experience with this community is (necessarily) limited. I'm sure you felt that what you were doing was another contribution, but due in part to this ignorance of how a community works, your efforts backfired for many reasons made abundantly clear on the current thread. Unfortunately, your subsequent actions do you little credit: in the process of seeking to understand and correct what happened, you (a) indiscriminately attacked the moderators of this site and (b) did so outside the usual forums provided for such discussion.
Your "several hours of salutary efforts" have not been wasted if it has helped you understand how this community works and how you can make constructive contributions in the future.