Maybe the content just sucks.

If the content on that community sucks, why doesn't that person block the community?

I don't like politics, especially US politics. There is too much of that content on the platform, and it drowns all the other type of content.

I blocked all those communities and moved on. I don't downvote all posts on those communities because "it just sucks".

If someone comes across an active well moderated community filled with on-topic content of an objectively high quality where everyone seems to be having fun, and that someone downvotes everything in that community every day, how is that beneficial? Why don't they post content they like? If they hate everything, why don't they block the community? Why are they spending time and effort to downvote so much stuff every day when it would be easier, and seemingly better for their mental health, to either block and move on, or contribute the flavor of content they want to see?

No one is getting banned for downvoting content here and there, but if they're putting effort in ensuring everything in a community is downvoted, they'd just be spreading illwill for no good reason :(

A good mod will help their community grow and flourish and have a good vibe. A mass downvoter who contributes nothing else is harmful to those things, and it makes sense a mod would want to defend their community against that.

Edit: kind've ironic that you simply downvoted both me and Blaze 😅