Earnings on your post can go up and down during the 7 days till payout. Anyone can upvote or downvote and don't need to explain themselves. You don't ask why bdvoter drop you a big upvote, then why would you question if someone downvotes you? The upvote didn't take anything away from you or damaged you in anyway.
I raised exactly the same question when I received my first big downvote of $6 many years ago. After someone explained to me that earnings are not mine till post payout, I felt totally fine about everything and accepted that this is how decentralisation works.
I don't necessarily care about the rewards, but a downvote like that simply triggers a negative feeling in you. And you ask yourself what you did wrong.
In addition, a downvote on Hive is rather “unusual” and that's why I think a short explanation would be nice.
Downvote is a feature of Hive, it's not unusual. Just like you have likes and dislikes on web2.0 apps. If you were a content creator on FB or IG or YT, you wouldn't get upset if someone 👎your content and ask them to explain their action. You'd probably shrug your shoulder and move on.
Please note, I'm not endorsing the dv on your post as I don't know what's behind it, I'm just trying to explain how things work on Hive. I see you started off playing SPL and moved into the blogging side, and that's great, we need people more people to dive into the wider Hive ecosystem. I hope this episode won't put you off Hive - you shouldn't if you understand how Hive works.
Don't worry, I'm still having fun on Hive and will continue to do so. The downvotes also have their justification.
Nevertheless, I would still say that downvotes on Hive are rather “unusual”. I don't know the statistics, but I would simply estimate that this is 99:1.
And I also find the comparison with YouTube somewhat difficult, as there are simply a lot more dislikes distributed here in general. (Are there still any dislikes on YouTube at all? I don't even know :D)
If you really must know, it's 0.245% 😊
Downvotes are primarily targetted for spammers and abusers, though sometimes there are collateral damage