A system organized with the expectation of trust and goodwill is broken when people "work the system". It is almost surely fraud, too: you failed to acknowledge an egregious conflict of interest, which everywhere I've seen asks you to do (when recommending reviewers). That you had to go through a third-party intermediary just highlights the degree to which this is fraudulent: you even needed to hide your tracks.

Do others do it too? Absolutely. Does everyone, or even most people? Absolutely not--"I think I know who this reviewer is" is one of the most popular discussion topics among grad students. Are you to be commended for at least anonymously admitting you were on the problematic side of it as opposed to doing it and pretending you didn't? Yes. Was this scientific fraud? Yes, almost certainly. The worst kind? No, as far as these things go, fabrication of results is far worse. (Also happens, but much less often.)

That you can exploit a system for your own gain to the detriment of society is not a virtue. Attitudes like this are why "we can't have nice things".

If we need to rework the system to avoid harm caused by somewhat-bad actors like you, well, so be it. We probably do. (We need to rework it for other reasons anyway.) But that in no way absolves you of the responsibility to live up to the social contract of the job (and the legal contract with whoever was putting on the conference--I guess this was a conference proceeding because of the "time slot" comment).