1. People want more money.
2. Remote jobs are becoming much more common as of late.
3. It is (much) easier to double up on remote jobs than non-remote jobs.
4. Doubling up on remote jobs results in more money.
5. Therefore, there is a growing movement of people who are doubling up on remote jobs. QED.
I mean, it's pretty unlikely that this argument doesn't hold. I feel like you'd need a citation to counter it.
You don't need a citation to counter a baseless assertion. My assertion is that most people who apply for remote jobs are fairly honest (by culture) white-collar types who wouldn't think to 'double up on remote jobs' for the same reason they wouldn't think go out at night stealing catalytic converters, which is that they possess a basic sense of right and wrong.
I mean, if you think that the average person is basically a scammer at heart, okay... Maybe you come from a low-trust culture, I don't know. I don't think most people who come from high-trust cultures would behave this way or think that behaving this way is okay.
But many more are now compared to recent history.
Stealing catalytic converters is directly harming another person and also punishable with prison time, it's hardly comparable to working two remote jobs. But sure, some (potentially large) proportion of white collar workers may not be willing to violate trust by working two jobs, but many would.
Beyond that, if you think that all knowledge workers are ethical people, I would remind you about all the horrible software that exists in the world for the sole purpose of scamming or harming people. There's a lot of it. And it's all unquestionably much less ethnical than working two normal white collar jobs.