Maximizing shareholder value is like a death grip that squeezes any public corporation into not making financial gambles on ethical grounds.
It's so important that these leaks go public for two critical reasons:
1) with that type of financial regulatory environment for public companies, the only way to create incentives for that type of consumer protection play is when it has monetary consequences if they do nothing (customers shutting down their accounts)
2) court docs from an earlier Yahoo trial in a secret court were already released when the NSA requested a huge trove of emails and Yahoo challenged it. I read the judges ruling and the TLDR is that the judge said the customers will never know their email is being read so how can you claim that a privacy violation has occurred?
The twisted logic here is that there's no damage to the customer/company as long as the intrusion is conducted in total secrecy.
So that's why Yahoo is so willing to fold here. This is what they are dealing with.
Side note: Imagine the same logic was applied to police a search warrant that allowed police to enter hundreds of houses, a type of warrant that could never be challenged by these homeowners defence attorneys. "They'll never know police broke into their house and went through all of their drawers and personal belongings. They'll come home the next day and everything will seem exactly. the same. So what claim to privacy violation could do they have?"
The need for secrecy in FISA courts goes well beyond protecting state secrets like NSA tech. This type of judicial rationalization would never withstand scrutiny in open courts which is why total secrecy is the key.