Google's motto of "Don't Be Evil," despite being replaced when Alphabet came to be, is still with the company in its philanthropy efforts and focus on transparency. Aside from some confidential company data, which still gets blown out of the water by third parties at times, Alphabet tends to shy away from keeping secrets from the public, allowing insiders, shareholders, and whistleblowers to know what the company and its sub-companies are up to. That focus on transparency extends to all sorts of government communications, including requests for user data from the FBI, and has led them to head to court and fight the obligatory gag orders on eight user data requests that they've received from US national security authorities from 2010 to 2015. They eventually prevailed in court, and have recently published the eight requests in question, along with the letters nullifying the requests' gag orders.
Google is by no means the first to publish inquiries from national security authorities, this is certainly not the first time that they've done so, and this certainly won't be their last time or any other company's. In recent years, many a company has banded together to not only fight the gag orders imposed alongside these requests for information from government agencies, but to actively pursue transparency by publishing these requests whenever possible. Some agencies have done the same in recent months, but the onus is mostly on the companies receiving the requests to decide if they should provide them to the public, should such be allowed, and then do so.
In the eight requests that Google has published, the FBI simply names one or two Google accounts that they need more information on. They don't provide any sort of justification, or why they're suspicious of the accounts in question. The letters included with Google's blog post have personal details redacted, such as what accounts the FBI wanted information on, or who was supposed to tend to the requests. To cap things off, Google vows that they will continue to stand up against government mass surveillance by fighting any legislation that expands what information the government can obtain or reduces transparency.