It may be simpler than that, one cause of rejection is you working in the US while not allowed. I keep hearing about people that get busted (most by the time they are reaching customs) by pictures or messages on their social media accounts showing that they worked (even just helping family) while in US on tourist visas.

So when I find my rival is visiting the USA, I can set up a linkedin with his name on and write "Working in Seattle for a few months as a plumber. $$$ is good here!".

And they'll be arrested?

I am not a lawyer but that could well be a federal felony.

Maybe you can prove them in person it is not your account, but that mean you would have to get a real visa not an ESTA.

Are ESTAs the one where applicants have to list their own social media accounts, or am I thinking of something else? Last time I went to the US was 2018, so even if I remember right, things may have changed.

I went in 2021, and I had to fill in social media accounts, they didn't say to which sites so I listed a whole bunch of them.

I just got my ESTA a week ago, there is a section where they ask for your social media aliases but it's optional and can be left empty. I did so and had no issues.