It really depends on the level of dislikes you're getting and also how you interact with others online. I've noticed that sometimes if we say things "controversial" on platforms such as twitter of facebook, and you have your channel linked to your profile, that can sometimes cause trolls to start attacking your videos which realistically, there's nothing you can do to stop that. This is why I try my best not to get into too heated discussions outside of YouTube. Sometimes we might say something on a popular video that trolls randomly don't like that make them come over to our videos to dislike.
There's also the trivial niche competitors, so your niche is boats, and perhaps there's another boat channel in your niche that sees you as competition, so gets their friends or alt accounts to try and attack your channel.
Sadly there's not much we can do about that. If the video content it'self is good, the content should speak for it'self regardless of the dislikes it might have.
As long as YouTube allows us to have multiple channels (and a lot do for business reasons) people will also use multiple accounts for nefarious reasons. It's best ignored and just hope the trolls get tired and move on.