Understanding disruptive griefing at immortal (7.5k+ MMR)

Main question: What motivates disruptive toxicity/griefing at higher MMRs (> 7.5k MMR) (e.g. feeding mid, outright AFK, excessive flaming, etc)? You see this occasionally on a pro's stream that they have an ally (or enemy) disrupting the game.

My thoughts – but interested in other reasons or angles.

Expectations:

1. You demotivate enemy players to continue playing. This reduces player pool and your queue times are longer.

2. You demotivate allies so you are avoided. This reduces player pool and queue times are longer.

3. You generally waste your mental effort expended on this self-aggrandizing and self-victimizing. This probably has some impact on your overall joy / pleasure with playing the game.

Reality:

1. No punishment/enforcement of any griefing, so people don't care that much about the above.

2. If you're at the highest echelons of MMR, you are comitted to the game and won't let one downer ruin your mood/game.

3. Verbal abuse is resolved by muting.

4. Griefing/afk is resolved by avoiding such that eventually there is a pool of healthy-ish players that don't engage in outright griefing behavior.

5. Smurfs/alternate accounts means people bypass being avoided/punishment.

6. Sometimes due to basically the nature of the game, any subsequent input is basically useless so better to AFK the game because you've already lost. Problem is here that it invalidates another player(s) hopes or desires to practice other gameplay related things or just attempt a miracle.

Looking for opinions of any kind – whether supportive or contrary.

Bonus question: How is it rationalized if you have pro players on your team or former TI-players and engage in such behavior?