There are many users who believe hive as opportunity where the skill are highly rewarded
Haha! Skill is not what the big votes are based on (they've said openly), and if you get too rewarded by others, those big whales will downvote you.
Downvotes are not totaly bad because it warns spam posters
That is the justification that's given for them, definitely, and that was the case back when Steem had over a million users. Hive with less than 20k users (besides Splinterlands) has much less of that issue.
and cleanse the hive ecosystem.
That does seem to be the goal. To cleanse it of any dangerous ideas.