They then converted the LPs gained into datacores, and did it again, because the value of the datacores was out or synch with the LP rewards. After this they moved up to implants, using manipulation in a dead system to artificially inflate the value of one item by gaming CCP's market algorithms. It likely wasn't noticed because no one was monitoring the market wherever it was going down (I'd guess in some dead nullsec station somewhere) because the base price from the shop doesn't alter they were able to create a discrepancy. At this point they were able to print LP and further exacerbate the discrepancy by throwing some of the now limitless LP into minmatar FW. The T5 modifiers they were able to buy made their final cash out pretty huge.
It's true that you could theoretically counter it if you saw it coming, or leech off it, but the cluster is too big I think to easily track exactly what they were doing.
honestly, anyone with access to a few billion isk (of which there are many) could do this on their own. These guys just did it first and with a significant amount of capital. the real issue is that it doesn't take that many accounts to shift the market like this, I'd say a minimum of 5-10, if CCP had say inserted a modifier into payouts which either forced daily diminishing returns, or diminishing returns for repeat kills, this wouldn't have been possible without hundreds of accounts, and nothing like the efficiency we see here.