Of course they are not really a mystery in the hard sense: we know somebody is trying to make loads of money with them which happens with many other coins as well. But I have discovered a pattern which I want to discuss in more detail here. It is this: Hive almost always pumps at midnight UTC. As Upbit (a South Korean exchange) has the largest volume of Hive by far and midnight UTC corresponds to 7 am South Korean time, we can be fairly certain that there is a group of traders on Upbit responsible for these pumps. But this is where the trail sort of ends with not too much more data available. However, we can also be fairly certain due to the amount of volume being traded, that this is not sustained by a small group of traders. However, it might be triggered by a smaller group.
We know that there are currently about 436 million Hive in existence. And we also know that about 163 million Hive is powered up (i.e., not held on an exchange). The largest exchange currently holds 82 million (Upbit), and the second largest about 24 million (Binance). There are 5 or so other exchanges where Hive is being traded, but they hold far less Hive.
The largest volume is by far on Upbit - a south Korean exchange only accessible by South Koreans. The amount of Hive traded there is truly astounding. For example, in March of 2021 there was a weekly trading volume of over 2 billion Hive. That is worth around 1 billion $ at an average price of about 50 cents! Since this trading volume and the change in price also affects the other exchanges we get a very similar volume and price pattern there as well. The second largest volume on an exchange in on Binance. For the same time mentioned above we had here a weekly volume of over 400 million Hive which still translates to about 200 million dollars.
In sum we can say that the often heard "accusation" that South Koreans are responsible for the pumps seems to hold true. With a roughly 9 times higher trading volume on Upbit than on Binance we can say that the price action and decisions to pump and dump the price comes from traders on Upbit. The other exchanges have far less Hive stored and as a result a lot less volume.
Here is the data (look at the right for the trading volume in "net volume"):
Now let's have a look at the pumps. For this I will be using the 2h as well as the 4h charts with different thresholds for volume that count towards a pump. For example, I will be defining a pump if the volume is greater than 450k Hive in the 2h chart. (Note: I did this for Binance when I should have done it for Upbit, but the results are almost identical so I didn't redo the work.)
I first set the threshold:
And then count the number of pumps as well as when they occurred:
I looked at three different time ranges (excluding the bigger pumps) which are: May 13 until June 2022, June 29 until July 21, August 3 until August 23
We can then count the frequency of those pumps at a given time. The x axis on this chart is time 0-23h and the y axis is frequency:
We can see that by far (!) pumps at this scale and threshold occur at midnight UTC with a second more distributed peak at around noon.
For the 4h chart I analyzed one time Period: May 22 until August 19
We can also see that here the pumps occur much more frequently at midnight with a second more distributed peak at noon. The distribution is just like for the 2h chart.
We can see that the pumps and dumps is very characteristic for Hive. All (most) other coins I looked at (with the exception of Steem) have a much more regular trading volume. There are spikes, but not as isolated as Hive has. This essentially means that Hive's price is unfortunately heavily influenced by South Korean traders and trading bots which is somewhat problematic as it shows that Hive is traded in a very centralized way.
What I would like to know is why Upbit ended up having this much Hive? Of course one reason is that they got the Hive airdrop when Hive hardforked from Steem. Perhaps it is because Steem was at one time a top 10 coin. It would then make sense that Upbit still had large holdings in that coin.
While we can't answer the question of "who" is responsible for the pumps (and dumps) directly we know that it happens on Upbit. This is a Damocles sword in my opinion: we can be fairly certain that we get more Hive pumps in the future, but we also know that they won't really be sustainable until Hive is traded with greater volume on other exchanges . This could also include the internal Hive/HBD exchange we have and will become more important once HBD gets a higher supply. We already know that all Hive holders would profit from a more decentralized distribution, but what I wanted to show with this post is that we would also profit from Hive being traded more evenly on many different exchanges.
The only real good advice for now seems to be to hold some liquid Hive in order to be able to capitalize on these pumps and not get dragged all the way back down again.
Tagging some people to whom this might be of interest (since I haven't seen this analysis so far): 
As a general reminder: Please keep in mind that none of this is official investment advice! Crypto trading entails a great deal of risk; never spend money that you can't afford to lose!
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