Which kind of investment was it though?
* An investment that makes something possible that otherwise wouldn’t happen. Like the US investing in NASA
* Investment that is not consequential in the big scheme except it makes people money.
Did his insurance investments keep some companies alive?
Generally the latter. The very short version is that he focused on cash flow, and liked (re) insurance due to success managing float and risk. From there, he'd buy/invest stable businesses and brands. Insurance wasn't his first go, he started bookie work as a kid.
As for saving, he was the guy with a big pile of money in '08 (and other times). Someone you call when your business is dying or you want to retire; he gets the deal, not you. His Bank of America warrant play was a big one from that time.
I didn't finish snowball, but the first half goes over a lot of it.
https://en.wikipedia.org/wiki/The_Snowball%3A_Warren_Buffett...
I think the right way to think about Berkshire Hathaway these days is that it's a highly decentralized, minimum viable civilization. They do everything from freight locomotives, to furniture-making, shoes, petroleum, chocolates and more. Then there's a layer of financialization on top of it all (insurance, re-insurance, loan issuance, market-making etc.).
If the U.S. became a failed state tomorrow, there's a genuine chance that Berkshire businesses would keep on operating and trading with each other, on Berkshire rails. It's like a hive of cockroaches -- businesses which are individually strong, that when woven together are un-killable.