The concept of the "sustainable war" was made by ghost in the shell 2045, and basically describes how a country can keep it's economy fueled by a small but dense area of fighting, creating high demand for arms, steel, high tech electronics like NOD's etc.
i believe the interest of BEAR isn't to investigate USEC's activity but to actively engage them were possible. the decree by the Russians not to see that the illegal activities stopped but that they were strained enough to make it worth for terragroup to continue regardless.
which is also why I believe Prapor has access to such specific weapons like good Ak-100 series and B variants, which aren't just found on the mainstream civilian market. i think he is getting sponsored by the Russian government to sell those guns, gear and equipment, and delivering a large percentage to the Russian gov, which is using the whole thing to keep their economy running.
same with peacekeeper. after the evac of the UNTAR mission force, peacekeeper either stayed or was left behind, and then got sponsored by the US gov to sell their weapons armor and equipment. how else is he able to get SOPMOD, or special operations purpose modification, variants of the AR-15. how else is he able to get good quantities of MP7, MP9 and P90 PDW's. sure they are civilian market, but they aren't cheap, nor found in any quantity in most military forces. they are used, but in special situations. so him getting access to such quantity and quality of US gear IN Russia, means he has to have a sponsor.
As for Therapist, i think she was a lead therapist on the health resort, which started working at the main hospital after the peace missions started, now realizing it has all become a monetary game, took over the hospital, and is now living off the PMC's health bills.
not to mention the fact you can escape the area, and get into a safe area where you can live, stash your stuff, rest up, and get back into the fight. and if it really was a humitarian issue why did the Russians not help out the UNTAR mission. or supply their own gov troops to the mission?
it's a sustainable war scenario.
my prediction also: Skier will get EU sponsored, and will sell FN and HK stuff directly, for Euro's, getting sponsored by the EU to also take a cut of the profit.
Source: https://www.reddit.com/r/EscapefromTarkov/comments/qrvbrd/tarkov_is_a_sustainable_war/