Musk but notes that only publicly available information will be collected, and not “DMs or anything private.” X no longer has a press arm, so there’s no real way to get ahold of anyone for more concrete information as to what data and information will be scooped up and what exactly it'll be used for.
X doesn’t have any public AI ambitions, He recently launched a company called, wait for it, xAI that aims “to understand the true nature of the universe”, so maybe your biometric data and related information will be used to further that lofty and totally achievable goal. Stackdiary points to that says it “will work closely with X” to “make progress towards our mission.”
There’s another option for where this data is headed. Musk recently stating that the employment site was “cringe” and that X’s version would be “cool.” So that would explain the collection of job and education histories from its user base.
Finally, there’s a third option. X isn’t exactly so selling user data would be an easy way to make some coin. However, there’s no evidence to point to that, aside from it being a standard practice in the social media world. In the past, Twitter primarily used and not third parties.