Well, I could tell you all about "they" but then "they" would have to eliminate everyone you have ever met, so "I" shouldn't take that chance. (That was "sarcasm").
I should know that trying to convince a paranoid person that there isn't a Conspiracy is useless, but here goes anyway... The "they" on scientific panels are people who are (or have) doing research in their fields and have been recognized by members of that field as being very good at their research. "They" are then asked by the editorial staff at a journal to become a reviewer of papers in their specific field. "They" are compensated for their time that they spend reviewing other peoples papers, because they could be using that time to do their own research.