I'm an anon who knows quite a bit about cryptocurrencies, having invested a lot of time in those.
First of all, I'll try to recompute the results of yours. I heard once in the media, that the entire Bitcoin network uses as much energy as a small European country-state (I don't remember which one).
Let's only compute Bitcoin for now, for the sake of an experiment. The current Bitcoin hash rate is: 24,785,843,885 GH/s[1]. That's quite a lot.
Let's (falsely) assume that everyone uses the most efficient miner available[2][3]. The miner uses 1480W generating 16TH/s. This would mean that the entire network consumes 2.1 GW. Now, multiplying that by 24h, we get 52 GWh. A year we get 18980 GWh. That would make it 1/1000 of world consumption and places Bitcoin electric consumption between Nigeria and DR Congo[4]. That itself is a lot and speaks volumes.
Surely, my computation describes only Bitcoin and in the most optimistic fashion. Let's assume an actual number is about twice as big, so now we get between Bangladesh and Philippines.
[1] https:// bitcoinwisdom.com/bitcoin/difficulty
[2] https:// www.buybitcoinworldwide.com/mining/hardware/
[3] https:// www.buybitcoinworldwide.com/mining/hardware/dragonmint-16t/
[4] https:// en.wikipedia.org/wiki/Electric_energy_consumption
The second currency is Ethereum, which is mostly mined on GPU for now (AFAIK), but Ethereum is about to migrate to a green "Proof-of-bet" scheme, akin to "Proof-of-stake", where you don't waste your CPU/GPU/ASIC cycles to calculate meaningless SHA2 hashes (like Bitcoin does in its "Proof-of-work"). Will that improve the situation?
In my opinion, not really, as the cryptocurrencies are actually a greed-based economy. In addition, Bitcoin was devised a long time ago and all recent tries to upgrade Bitcoin resulted in forks and disagreements in addition to boycotts by the mining industry (which itself has grown really big). If Ethereum happens to migrate (without a miner boycott) it may cause a flood of cheap GPUs… to be reused in other mining… or AI endeavours. But it's just Ethereum.
I used to be interested in cryptocurrencies at large, seeing as they are a) easy to use, b) free people from a need to use banks. Now I see it's not much better, it's yet another banking scheme, but a much less regulated and a lot less greener. What is more, I'm quite afraid, it will be used by the General AI. Right now I see that the only way to fix economy is to get rid of a so-called parasitic element, but at that point of time we won't actually need money at all. How can we do that? Maybe by creating small societies that are possible to be guarded against the enslavers. I'm a big fan of unregulated money schemes, because I'm a freedom fighter, but they won't work while we have at least one parasite (and by parasite I mean an unethical member or otherwise a criminal - well, they are allowed to use the banking system as well, but in the second one they may be regulated).
Did crypto actually bring some kind of freedom? Yes, of course. It also created fresh billionaires, who aren't related to the cabal. It also created a lot of people who lost everything (look at all those failed ICOs). It also allowed a lot of new high-tech crime possibilities (see eg. ransomware). I'm sure one day cryptocurrency technology will make country states much less needed, itself freeing people a lot. But, as of currently, it won't free us from the banker supremacy, it will just create new bankers - independent ones, but they are still likely to form a new cabal. In my humble opinion, people need to look at money in a different way, mostly as a mechanism of value transfer, not a hoarding scheme and that loan resets should be a tradition, possibly with a way to issue your own bonds and a locality preference. I don't see how that can be possible with Bitcoin. But well, I'm a dreamer… or rather I'm fed up with banging the wall with my head trying to stop and reverse the current trends of ultimate centralisation of everything.