I'm pretty familiar with what GS does...and plenty of experience in thin market, thanks. Structured products are a very different thing than what you were describing earlier which was becoming a significant percentage of the daily trade size for a product ("But look at microcaps or OTC stocks, hell still even crypto...if you keep buying untill the shorts puke and the trendfollowers jump aboard, you got yourself a nice trade...happens all the time."). An i-bank makes consistent products in structured products because they charge a spread on the product, not because of "trading" savvy. In fact all their trading savvy is applied to trying not to move the market as they lay off risk. And they're not "whacking" anyone with a structured product trade, why bother when you're making such a consistent and large profit on simply putting together the product and laying off the risk. What you're describing is prop trading, which doubtless a few frustrated i-bankers till try to engage in post Volcker Rule under cover of structured products. But since they can no longer tie bonuses to prop trading profits, the motivation to break the law on the part of a trader really isn't there any more.
This vast conspiracy of big market players manipulating markets to profits is a convenient way to justify poor performance in the mind of a losing retail trader. Unfortunately there just isn't a lot of basis in fact for it given that they really want the opposite. They certainly have conspired on things like LIBOR fixing, but it's not where i-banks consistent profits come from.