Don't worry, these are the "keeping the bridge intact" speak of people leaving a glorious or so workplace. I have worked at several places, and when people left(usually most well paid ones), they post linkedin/twitter posts to say kudos and inspire that, the corresponding business will be in forefront of the particular niche this year or soon and they would like to be proud of ever being part of it.

Also, when they speak about AGI, it raises their(person leaving) marketing value as someone else already know they are brilliant to have worked at something cool and they might also know some secret sauce, which could be acquired at lower cost by hiring them immediately[1]. I have seen these kinds of speak play out too many times. Last January, one of the senior engineers from my current work place in aviation left citing about something super secret coming this year or soon, and they immediately got hired by a competitor with generous pay to work on that said topic.