> The premise that visible business failure harms brands is false.
Given that many forms of visible business failure literally cause brands to cease to exist, it seems indisputable that at least some of the time they're harmed.
Some of the times they're harmed, some of the times they're not. There's no correlation, ruling out the slightest possibility of causation. Is it risk management, then? No, because a product with a well known and trusted brand has much higher chances of success. Is Google internationally reducing the success chance of their billion dollar bets? No. The only reasonable conclusion to make is that Google doesn't want to taint their new offerings with the existing brand.
What you describe in your first sentence is a correlation. Additionally, risk management sometimes involves preventing things that have never happened before.
We may just have to disagree on the value of Google. It seems obvious to me that it is a critical asset to Alphabet that must not lose search/product share before another Alphabet subsidiary pays off. I believe the purpose of spinning companies out of Google is more about improving capital allocation than protecting either brand, with the possible exception of Waymo if there is a huge backlash against autonomous vehicles.
"Some of the times they're not" does not exclude a potential correlation.
For example: "Some of the time, going to the hospital will not make me better, therefore there is no correlation between going to a hospital and getting better"