germany is certainly more advanced than the US in regard to responsible corporate governance.

governments taking equity positions in corporations can be bad because of the risk of corruption, self-dealing, and regulatory capture, not the principal-agent and subsequent sunk-cost risks you mention, imho.

unlike other shareholders, governments aren't strongly motivated by attaining the largest return for themselves, particularly since taxes and bonds are much easier revenue sources. and in crisis, the government has the negotiating leverage to stipulate stricter conditions upfront that aren't normally part of non-crisis investments.