$900M/year is <1% of Alphabet's yearly revenue. I know you mentioned profits, but the OP mentioned revenue so I want to keep the same units because they're very different things. It could very well be that if it was $20M/year in profits, then those projects would not be considered failures.

If something happened to their core business, it's unlikely that those tiny projects (<1% of revenues combined) would save them. The more likely thing is that many of those small projects fail over time and it becomes death by a thousand cuts.

What you said is mostly correct and is exactly what they are doing. The only problem is that at the scale of a trillion dollar company, they need 10, 20, even 30 business lines generating $XB - $XXB of revenue each.