That’s not enough, still. It should directly affect the rank too.

I disagree. I think they made the right call to make behaviour score and rank seperate.

Because rank is everything to those toxic people, it is the only thing that drives their toxicity.

Not true, I play a lot of unranked and there are many toxic players there as well.

But they made a mistake by making the rank public, because now the players are no longer playing for fun, they are playing to raise their rank

Same as before, people play to win regardless of there being a visible rank or not. The game is competetive either way, and competetive games attracts toxic people.