This sounds like a common variety of crypto scam. It works just like any fake investment scam or ponzi.
They may be getting nothing, or they may in fact be getting "real", theoretically useable crypto, but the coin they are getting is worthless and the founders of the coin are the ones collecting these "mining" investments.
If they are getting something actually worthwhile, like bitcoin that is in his own wallet controlled by himself (not the "investment company"), it may be legit or it may still be a ponzi.