Toxic behavior has a double-edged consequence. It both tends to make the person responsible feel like they act that way naturally, and it also makes people respond to them as if they act that way naturally, it becomes a feedback loop. So much of the perpetual cycle is subconscious.
Sometimes it takes a hell of a lot of patience and a step back to say, “you aren’t toxic but your behavior certainly is.” It’s moments like those where maybe, hopefully they can realize that behavior is something for which they need to seek proper help.