Toxic vs Troll. Whats the difference?

I don't understand, you ban players for life for being "Toxic" but don't ban players who play Disco Nunu and are there to just make the game miserable for the other 4 players on his/her team. Why are Trolls rarely as badly punished as toxic players? To stop a toxic player for a while you can ban them from chat for 50+ games. To stop a troll the only way to do it is to completely ban their account, which by the way never happens. An example is Dunkey's new video. Now i know Dunkey was extremely toxic and deserved the ban but what about the other guy who went 0/9 as Malphite and clearly intentionally fed? Or my friend getting banned for calling a kid a retard when the kid was 0/24 as Yi and was turret diving level 18's as a level 4 after he AFK'ed cause he saw it was someones promos for plat?

Riot, you've made mistakes in the past like releasing broken champs, broken items etc but the worst thing you have done has been solely focusing on Toxic players instead of focusing on the players who literally ruin/waste someones time for 20+ minutes just because they feel like it or because they had a bad game and are upset. Implement a new system like you did for Toxic players for trolls so that the league community can feel like you guys are listening to them for the first time cause frankly what you have shown is that you literally have 0 respect and don't care about your community and only listen to us when it benefits you. I.E new skins/new champs.