In a proper capitalist society the government defines the rules of the market, aligned with the interests of several parties, and then companies compete within that well regulated and fair environment. The only incentive the government should have is to grow the entire market, so that they can collect more tax. There might be minor exceptions to protect key industries like food production or defense, but these should be a small as possible to ensure healthy competition.

It’s something entirely different when the government starts taking a stake in individual companies instead of the market as a whole. This can easily bias the government to pick OpenAI for certain contracts, or enact laws that benefit OpenAI more than its competitors. It reduces competition which hurts the overall economy, and it is an obvious vector for corruption which hurts the efficiency of the government.

It’s great if we can leverage AI to design the next great government system. A 5% stake feels more like a bribe to help push through some of these datacenter projects and enact friendly laws.

This is a vision of 'proper' but certainly not the only one. Another version many of the very rich would like to see is given below.

In a proper capitalist society the capitalists define the rules of the market by competing to own the most politicians. The capitalists best at buying political influence get a larger say in what the rules will be so as to align them with their specific interests regardless of damage to others. When rules are aligned to your specific interests, this is called a well regulated and fair environment. Otherwise it is called a repressive nanny-state deep state swamp. The only incentive the government should have is to grow the politicians' personal wealth by bargaining with capitalists for which policies get enacted. There are no exceptions to protect key industries like food production. Defense spending is, however, in most capitalists interests as they often need the use of violent force to eliminate or subsume competition in other nations. Defense will therefore always receive robust funding.