1. the "countries" will never buy cryptos. specially not altcoins. nobody wants to put their money in shit unless you are small time investor wanting to make quick profit from pump and dumps.
2. there is this law in many countries (some of which are among G7) that prohibits banks from investing in any sort of cryptocurrency.
3. you say THEY are dumping to crash the market, that suggests they already are whales with a lot of coins. so why would they want to buy more? they can make a lot more money by just pump and dumping in this area, there won't be any "bull run" if your theory is correct.
4. there is a much easier way of making a LOT more money. and that is creating their own shitcoin. for example something like ETH which already has the bankers behind it and make millions of dollars from its premine/ICO shit and the the follow up pump and dumps.
Lets say for example when the bitcoin was at 10000$ last year they may have bought the bitcoin with huge money and took the price of bitcoin to its ATH and we small investors also bought in FOMO and now they are dumping in 2018 making continuous decrease in its price in 2018. May be they do it every year to make people lose confidence in crypto beacuse they are afraid of its potential .