> I don't get how Account B gets to the point of extracting value from the illiquid asset after purchasing?

My understanding is, accounts A and B are both controlled by the same person/group. Account A always deals with clean money and pretends to do speculative investing; account B uses dirty money to pump illiquid assets. An example scenario, as a simplified list of transactions:

  | Time | From    | To     | Amount     | Note                                      |
  |------+---------+--------+------------+-------------------------------------------|
  |    0 | Pocket  | A      | 10 $GOOD   | Initial investment.                       |
  |    0 | -       | B      | -          | Created account for criminal activity.    |
  |------+---------+--------+------------+-------------------------------------------|
  |   10 | A       | Market | 10 $GOOD   | Exchanged liquid $GOOD for illiquid       |
  |   10 | Market  | A      | 1000 $BAD  | $BAD at 1:100.                            |
  |------+---------+--------+------------+-------------------------------------------|
  |  100 | Victims | B      | 3000 $GOOD | Crime - e.g. ransomware payments.         |
  |------+---------+--------+------------+-------------------------------------------|
  |  150 | B       | Market | 3000 $GOOD | Buying up $BAD to generate interest and   |
  |  150 | Market  | B      | 1500 $BAD  | pump its value.                           |
  |------+---------+--------+------------+-------------------------------------------|
  |  200 | A       | Market | 1000 $BAD  | Buying back $GOOD for temporarily liquid  |
  |  200 | Market  | A      | 5000 $GOOD | $BAD at 5:1.                              |
  |------+---------+--------+------------+-------------------------------------------|
  |  500 | B       | Market | 1500 $BAD  | If $BAD didn't collapse, recovering some  |
  |  500 | Market  | B      | 100 $GOOD  | of more stable asset at 1:15; can be used |
  |      |         |        |            | to repeat the trick later.                |

In this scenario, criminals turned $3000 of dirty $GOOD in account B into $5000 of clean $GOOD in account A. If they were good with OPSEC, there's no connection between accounts A and B - from outside, it looks like the owner of account A got lucky speculating on crypto, and owner of account B was a dumb criminal that made a bad investment. Hell, if criminals are sure of their OPSEC, they could even go as far as paying taxes for their gains on account A, reinforcing the image that A is owned by some random, legitimate investor (but that could bite them hard if law enforcement realizes there's a connection between accounts B and A). Account B is never cashed out - it's used only for purposes of pumping illiquid cryptocurrencies, and eventually abandoned.