is sandbagging illegal?

Sure, sandbagging is cheating. Rating manipulation and it will most likely get you banned.
Yup, I got closed for rating manipulation

CrusaderKing1:Yes it's illegal. Punishable by 9 months in prison.
I don’t think that is true because breaking the rules of a website is not illegal, so there are no legal consequences, the only consequence is that your account gets closed.
If you play for money, it might be illegal.

oh, poo.
its against guidelines but chess.com really doesnt care if you sandbag form my experience. Go buck wild and the chances are if you play a few games inbetween resigning they wont ban you.

Its against the rules but if you just spam new accounts they cant catch you so its not enforced enough.

You are supposed to ask permission for a speed-run account, but I still do not think it is fair, and certainly a player should be allowed to abort if he knows he's playing against a speed-runner, or could have a setting to simply never be paired with one.

Once I tried sandbagging by resigning on the first move for 6 games, chess.com banned my account for 1 hr, so I never sandbagged again.

I think the best way to sandbag is to play like an idiot or random generator, not resign on the first move.

The leagues need restructuring, and actually made to mean something, once you get to legends league there is no magic rainbow it's just a brick wall no tournaments or cups to play for, people dedicating their valuable time getting there only for it to be utterly pointless.
What real incentive is there for anyone to sign up and pay for a membership when they can't even put on a monthly tournament like they did before

it's very annoying watching them 1200s farm points in leagues. it's inherently unfair to higher rateds like me. so. my plan is to sandbag my blitz and grind all the way up to legends. is this gonna get me banned by Chess.com?
the best way to grind points is to get in a bullet tournament as those give a lot more points.

Hi
Sandbagging isn't allowed any members should be reported
https://support.chess.com/en/articles/8562517-how-do-i-report-someone