Asklemmy

You look at it as a social media platform. The people who run bot accounts, have specific goals they want to achieve such as swaying public opinion on a specific topic. They could have been paid by a corporation to do damage control on a negative event that happened.

When they downvote you and upvote their other bots, their content gets higher visibility.

Don't forget about other unnoticed tactic, redirecting your attention to something that has nothing do to with the subject, just to make you disregard entire discussion or pay attention to something different. It's subtle but happening all the time, now you'll see it everywhere.

Why, I haven’t been so insulted in my life, being compared to a bot. It’s me.

The instance admin can see votes. If you are noticing a pattern maybe ask them to confirm? There can be delays in federation so you might see them all come in at once even if they occurred quite a bit earlier.

I know your question was "why" but maybe confirming that is that is happening vs a different cause can be the first step.

I don't care about the downvotes. I intentionally view ALL posts in the feed, I don't hide anything just because of low score. The lowest score might be the best!