All of those government organizations are under the same management: the government. Subsidiaries are still under the management of the parent firm.

No idea how the military analogy works but: large companies scale up by "in sourcing" their supplier's functions. Facebook collects their own metrics instead of using datadog. Their own logs instead of Splunk. Facebook's own high cardinality traces instead of Honeycomb. Own datacenters instead of buying from AWS. Own database(s) instead of Oracle.

And then, since you have all these integrated functions, you can spend headcount optimizing datacenter spend down. Hire a team to re-write PHP to make it faster literally pays for itself. Or kernel engineers. Or even HW engineers and power generation. And on the product side, you can do lots of experiments where a 1% improvement in ad revenue pays like the entire department's wages for the year. So you do a lot of them, and the winners cover the cost of the losers. And you hire teams to build software to run more experiments faster and more correctly.

The brakes on this "flywheel of success" is the diseconomies of scale outweighing the economies. When the costs of communicating and negotiation are higher internally than those external contracts you previously subsumed. When you have two teams writing their own database engine competing (with suppliers!) for the same hires. When your datacenter plans outpace industrial power generation plans. When your management spins up secret teams to launch virtual reality products with no legs.

I've never been in the military but I'm told they work this way. You often have interactions with people across the org chart (which is a massive tree with >100,000 nodes on it). If there's a dispute over resources or requirements that can't be resolved you need to find the lowest person that is above both of you to settle it. The depth of the org chart is a key similarity here as well. I think I was ~10 degrees from Sundar when I worked for Google. A soldier in the US military is a similar distance from the president. Also the financial numbers that are thrown around are larger than what most governments deal with and on par with even large nations. The US military might get a $100B influx for some war. Google/Amazon/Meta/etc. spend similarly on AI initiatives.