Leaving vs DCing

In a game of league there's nothing more frustrating than losing because of something that's out of your control. I think it's also fair to say, most if not every player would want to not be banned if they disconnect via some problem with internet or power outage, etc... But when a player clearly disconnects from a game because they do not want to play it out. They should not be punished as though their internet just went out and it was out of their control.

In my last game I met 2 players that were willing to leave the game at 1 minute into the game because 1. It's preseason so they don't care much about getting a lose and 2. A player died during the enemy team's invade because they weren't paying attention. Leaving for these reasons at the start of the game where the winner is clearly undecided is extremely toxic. They should not be able to just re-queue up after the game is over.

https://matchhistory.na.leagueoflegends.com/en/#match-details/NA1/3213000546/47054537?tab=overview The Evelynn and Yasuo ^

As you can see in the match they made no effort in the game and me and 2 others got a free lose and demotion because of it. Players like this should face harsher punishment to dissuade this behavior. I think if there's chat logs that clearly show that the player is leaving because they are frustrated or something with the game and unwilling to play, they should be banned from ranked games for at least a month. Saying something like "open mid, have fun" at 1 minute in and disconnecting, I'd say is quite enough information for a hefty ban.

Is there anyone that can shed any light on situations like this and how riot determines their bans?