I think the dire state of the German economy might prompt a question: Could investing in BTC help improve the German economy?
I don't dare to give an answer as anything can happen in the future, both positive and negative. As a BTC and crypto enthusiast, I think the German government should take advantage of the crypto wave to collect crypto taxes, supplementing the government budget to support the economy. Using the budget to reserve BTC comes with many risks but is also worth experimenting with on a small scale if the German government wants to leverage the price increase of BTC to generate profits to rescue large businesses instead of facing the general inflation of the EU.
If nothing has changed (and I don't think it has), in Germany the tax on the sale of cryptocurrencies is 0% if you sell cryptocurrencies 1+ year after you bought them - so I don't believe that the German government has ever gone in the direction of making any significant money from taxing people who invest in cryptocurrencies.
They probably count on the fact that the profit from such investment will be returned to the system in one way or another, either through VAT, increased personal consumption or perhaps by starting a personal business that will perhaps employ additional people. Unlike some countries that have taxes up to 55% or at levels of 20-30% and thus actually discourage people from investing in cryptocurrencies, Germany has a very good model in my opinion, along with some other countries within the EU that have similar taxes (or they don't have them at all).
In addition, it should be taken into account that Germany is part of the EU and that European finances are controlled by the European Central Bank, and accordingly, no country can buy BTC and keep it in its reserves just like that. I am not 100% sure that this is the case, but I know that when it comes to gold reserves, no country within the EU can sell gold without the approval of the ECB.