How would splitting Instagram work from a technical perspective? Engineers have spent 8 years building shared code and data centers for FB and IG. I'd expect it would take hundreds of people and multiple years to untangle them.
Facebook has been trying to make it appear that integration will make separation impossible.
But the reality is, you simply duplicate the databases and whatever shared services they depend on, and create a "stub" FB backend for IG, and a "stub" IG backend for FB for the shared services to work... and they go on their merry independent ways, while engineers remove things that depend on the stubs at their leisure.
Obviously it's not trivial (and involves the inherent complexities of any datacenter migration), and doing it without downtime is a whole separate beast, but it's not impossible or so wildly difficult it can't be carried out. In other words, there's zero reason it should be a factor in the legal outcome.
At most, there would be an IP issue -- e.g. would the spun-out IG be permitted to have a stubbed FB backend, and vice-versa -- but that's easily solved by providing those permissions as part of the separation agreement, with a timeline to remove them (e.g. 2 years).
Replicating and building out an ad platform like FBs from zero would be very very hard. None of the other social platforms ad networks are even close in quality but especially interface/targeting/features. Snap / TW I would say are at maybe 5% if I had to pick a number...
Especially especially taking into account integration with FB pixel.