@khansab Yes I totally Agree with you that if we are talking about CASUAL games there should be no punishment in intentionally loosing by either side ... wortst case scenario just being silenced from automatically joining games for e.g 30 minutes or so (just to filterout ppl that do intentionall stupid moves all the time which yields in other people not getting any joy from their games) but certainly not ban the account all together!
Having said that I think (and again that's just me I dont have any way to know that just my feeling) that lichess maybe thought that the oponent lost intentionally to you which lead you getting some points because, yes you are higher rated than your oponents but in some games I checked out by the link you provided they do a series of very bad and unconventional moves even for their lower raiting that lead them to be check mated e.g
here
lichess.org/92FQQdfk/black#28White here starts by pushing the e pawn to its demise move after move (didnt even capture with en passant) then after the pawn "suicide" he just "suicides" his knight without any sort of logic (it didnt seem to attack anything other than a pawn and didnt capture any pawn by moving it to e5) then he does some equally baffling moves like after suiciding a pawn and knight (and we are still on the opening phase of the game) he chooses to move his king towards the center and then eventually gets checkmated...
Which is a very ... how to say it politely ... questionable set of moves I mean I doubt even a 1000 rated player would do that this is something that only a player who just learned how the pieces moved might do but then again its hard to say if even that player would play that bad.
Or this game:
lichess.org/EnwFf5bR#33I mean what is this? this isnt a 1800 player...
On move 5 he blunders the knight and then next move blunders an other knight without getting any advantage even if you decided to spare his 2nd knight lol
Then he proceeds blindly moving his pawns (and to the worse squares possible e.g on move 8 he could move his pawn to f6 so that you could NOT place your knights to g5 or e5 yet he chooses to push two square forward to f5 doing absolutely nothing and defending nothing just creating holes in his structure) until he gets mated...
That's not 1800 play not close...
And I didnt check all the games I just chose two games (the above mentioned) randomly and if the other follow that "nature" then I think there might be a reason to question you.....
In other words it is quite possible that lichess thought that your opponents lost intentionally for you to get a higher rating.
EDIT: And just because I thought that maybe I got "lucky" picking randomly those two games I clicked a third one
Which again is of the same "nature" as the others above, I wont spend time looking at all 43 games but I am afraid that a pattern starts to emerge.....
On move 5 (a 1800 player) plunders his knight in the center of the board, being unprotected and not attacking anything other than an already defended black knight....
Then on move 7 you(black) plunder your knight but white doesnt retake.... but lets assume it was "too hard" to see the check with the queen (although its a 1800 player anyway)
Then on move 13 white just leaves his rook for the takes.... you didnt get that rook though because you decided to move your knight to the H file + the knight is unprotected there... which is a rather bad square but it seems that you can see into the future and guess that White will not do anything about that and mate him using your queen (talking advantage of your unprotected H file knight defending the g2 square so that the Queen can deliver mate)
Then on move 14 white keeps not caring about his exposed rook that is still attacked by your blacksquare bishop instead he decides to plunder his white bishop for a pawn at b7 (which also granted your whitesquare bishop a nice diagonal towards the exposed king) and eventually you take that rook as well
Then on move 16 you move your queen to the 2nd rank threatening mate and white does nothing to stop that (e.g moving rook to f2 attacking your queen and holding everything at least for some moves) instead he decides to move his Queen ONE square doing nothing (not threatening anything or being able to get closer to the king etc) and then you mate him
These would be curious decisions even for a blitz game but it was a 15 minute rapid (and I think the other ones where also not blitz games) which increases the "strangeness" of your opponents moves exponentially especially when taking into account that he has a 1800 rating.