One of my answers (deleted now, 10k rep only) had a score of -8 within 10 min or so. I don’t think this is possible. My answer may have been wrong but it’s unlikely that that many people would see it so soon.
I doubt you were the victim of unwarranted downvotes. I actually wanted to downvote but couldn't because it was deleted before I got there. While I don't want to seem overly negative, I'd like to explain why I would have downvoted it from a regular users's perspective (not as a mod), and I strongly suspect these are also reasons that others did so before the answer was deleted.
Your answer implied rulings contrary to the rules as written and the rules as intended by the designers, so it was counterfactual and looked like an uninformed armchair ruling.
Your answer included no citations or rules in support of its ruling, so there wasn't enough to comment on to elicit you to improve it, leaving downvotes as the easiest remedy.
Your answer was very short and failed to include an actual answer to the original question, which is how to resolve the spell, so the answer wouldn't have been enough for the original question poster to be able to resolve the spell even if it weren't counterfactual.
The answer was quickly drawn to the attention of many people. See @nitsua60's answer for an explanation of the tools and venues that brought this about. However, as a regular user I can confirm that your answer was brought to my attention multiple ways: I saw it while posting my own answer, while revieweing other answers, while reviewing the low-quality flagged queue, and at the top of the QA listing for D&D 5e due to the frequent updates to the QA as a whole.
Don't be discouraged, but try to learn from the experience. The next time you post an answer, consider what support it needs and whether your post will be helpful enough for the person posting the original question to solve all their problems. I think it should be fairly clear in hindsight that your answer would have left the original question poster scratching their head for lack of insight.
Also, you can't see them (it requires 10,000+ reputation), but there were 2 other counterfactual answers to the question that also got enough downvotes to prompt the mods and/or those who posted the answers to delete them.
This is the place to come.
Raising the issue on meta flags it to moderators' attention and creates a nice starting-point to and container for any investigating we or, in a serious case, the SE staff would have to do.
I will say that a few things argue more in the direction of "this could be natural behavior" than the question here indicates.
- The question your answer's posted on has over a thousand views--eight downvotes on an answer isn't out of the realm of possibility.
- Another answer (10K only) got a similar number of downvotes in the hour before it was deleted, simmilarly-timed to yours.
- One of those downvoters left a comment explaining their reasoning (10K only again)--that would be really-unusual behavior for a sock-voter, as "leaving no trace" other than the vote would most keep them under the radar.
- Your answer was flagged as low-quality, bringing it into the review queue and in front of high-rep users' eyes more quickly than it might have been otherwise.
Using the tools we moderators have it's... inconclusive. Frankly, you haven't been active long enough nor have had enough votes cast your way for the system to start including you in the cross-reference reports. So we can't (yet) see if votes coming your way are from the "usual suspects"--high-rep experts in the tag you posted in who are daily-active--or from some suspicious collection of accounts.
If, after some more activity, you still feel like downvotes are coming suspiciously fast do post again or ping one of the moderators in chat to look again.
Oh, the sacred flame vs swarm question. Nope, looks legit. New 5e questions get a lot of views, the top answer got 27 votes, and there’s other rules-wrong answers that pulled a bunch of downvotes too. Sorry, citing rules incorrectly pulls quick wrath on D&D questions.