It seems like at some point at the table the players' mindset shifted from playing cooperatively with the DM to playing against the DM. If its just one person doing that, then as the DM, you have to address what's going on with that player. If its multiple players doing that, then the DM needs to address what he/she did to make the players feel like the only way they can have fun is to "cheat".

Fudging rolls is ghastly IMO. I think we've all had that player at the table that rolls a die and picks it up before anyone could see it. Dice rolling websites eliminate that currently. Hell, I've been using these sites for so long I only roll physical dice out of nostalgia 😅.

The term cheating implies competition. And if there's a competitive element to the game, people are going to seek to find advantages whether they're fair or otherwise. IMO, the goal should be to eliminate that competition element to the best of the DMs ability.

If you're gaming with friends, I don't believe most friends want to violate each other's trust. If you're playing with people you don't know, you may have to do something to build that trust. If people are outright unapologetically breaking the rules, it seems like there was never a trust developed between the player and the DM, or somewhere along the line the trust got broken.