I don't know too much about what happened after that, but I suspect not having control over the money making apparatus made it hard to control their destiny, and now we have Verizon owning them and finishing up the death spiral.
I encountered a ton of cool technical solutions to things that were Really Hard Problems in the 90's or 2000's, and that was appropriate for hardware from that era, but the outside world moved on, while everyone inside Yahoo still thought that their shit was hot shit.
There were for sure a lot of smart people still working at the company, but the company had 0 cool factor, so they had an incredibly tough time recruiting and retaining people that could move the state-of-the-art forward.
...and no buzzword management strategy like OKR's or whatever is going to change that fundamental problem.
Google does seem to sabotage a lot of its products, but so far hasn't really sabotaged its core products or its company. As long as they don't destroy the dollar printing press (Adwords/search), they can keep pissing away money on dumb things and it won't kill them.
Shame, because that was the one thing they were quite good at at the time.
I think the existence of other companies that were in similar starting positions, and then subsequently failed, would prove that you need more than just that starting position to succeed.
What allowed them to 'win' in that space decades ago? I don't know, nor do I feel the need to know in order to just much more recent history. It could have been organizational structures that either in a different time, or with a different group of people, or at a different scale, or whatever, were the key. Or something else. I have no comment on it.
But I have a very limited view, having lived in SF for a few years and just having insight into the companies I've seen. I bet there are loads of them that I'm just ignorant to.