I don't really have much to add to this post except for what the title already says

The Help pages have an answer for you:

What is a Sandbagger?

A sandbagger is a player who intentionally lowers their rating by losing on purpose, often with the intent of entering tournaments that they can easily win. Sandbagging is part of a broader category of rule breaking called rating manipulation, which includes fixing game results by arranging games, playing with multiple accounts, or losing intentionally.

If one player has completely dominated a tournament, and seems to be playing way above their rating, take a look at their game history to see if it looks suspicious. 

Hover over the user’s name, and click on the ‘archive’ icon (sometimes you may have to click on a ‘more’ option first to see this icon)

This option will take you to the player’s recent games. 

Sandbaggers will often resign many games in a row after just a few moves, lowering their rating by a large amount. Sometimes these players will give away their queen before resigning, to make it look like they resigned due to a blunder or misclick. 

If a player has a long string of losses right before they entered a tournament or a club match, they might be a sandbagger. 

Sandbaggers don't always sandbag to enter tournaments! Sandbagging is against the rules whether they are going into a tournament or not. Some sandbaggers just want to win some easy games, and will lower their rating to play lower rated players in auto-match. This is still against the rules! 

If you have played against someone who seemed way stronger than their rating, and you look in their game history and see a long string of losses in just a few moves before they played you, then that could be sandbagging!

If you suspect someone of being a sandbagger, please report them! The fair play team will look further into it. 

https://support.chess.com/article/208-what-is-a-sandbagger

cheating forum?

thanks for the help!

When I played in over the board tournaments where there were cash prizes for the winners, some would lose games on purpose to lower their ratings so when they played in bigger tournaments for bigger prizes they would be able to play in a lower class and win significant money. I remember playing at a tournament at Kennesaw, GA in the early nineties rated over 1400 and a guy who walked down the middle of the board and checkmated me with no effort whatsoever on his part. I immediately knew he was much stronger than his rating indicated and told him so and he freely admitted it. I won second or third in my class but he knocked somebody out of a prize that actually deserved it.

I can see the financial motive in someone cheating in that manner but what purpose does it accomplish playing online chess with no money involved?