I did a bit of trading in the SC Grey Market but my RMT experience came from several years in Warcraft, Aion etc farming and selling currency and buying accounts.
In 2014/15 I looked at the SC Grey Market for the first time and it was obvious then that there were a few very well stocked "stores". You only get to that position if you have access to people wanting to sell their assets and there were not that many sites around mirroring reddit (in English).
You wondered where they were getting their supply from and why people would be willing to risk losing their ships/accounts when the sums involved were so high.
It is one thing for a teenager to level an account up then decide to sell it but another for an adult to want to sell a SC ship for a game not released and potentially worth more when the expected game is released. Sure there are some people that would want to liquidise their assets but not that many and it all represented a significant risk for the people buying them and holding stock.
If they are stolen from accounts or you have gotten them free the risk of an actual monetary loss is obviously a lot smaller. As it is operating as an agent or other middleman putting a seller and buyer together but that also implies a much more time consuming arrangement. You have to find people willing to sell, gain their trust and go off and do work to find buyers etc...
So it is plausible that people with large lists of ships for sale were either hacking accounts, or otherwise getting them free.
Then you have the money laundering side .
someone like Ben wouldn't have the experience to manage an operation like this unless he had been trading in other markets prior to SC. He also wouldn't have the time or the inclination if he was working for CIG.
What would be more plausible to me would be someone outside approaching certain SC staff and coming up with an arrangement to buy ships/accounts on a regular basis or bumping into them when they were selling say one of their own ships (possibly legitimately as far as their Employment Contract was concerned) then that escalating into a much more serious/regular arrangement that made them a useful income on the side.
People of Lesnicks age that have a career are less likely to take a risk like this but Ben hadn't had a typical career so perhaps he lacked judgement. He would maybe have had access to accounts early on because processes were not in place to protect accounts particularly from employees or prevent them being created with a supply of free ships by someone on the inside..
If he was getting slighted and falling out of favour he might have been tempted later on in his SC career..
Anyhow in the absence of evidence it is all speculation.