the only thing I've seen that makes sense out of what they did is they have been angling for a sale, and offloading all the "losing" studios was a way to make the sale look better. I don't know who the fuck would want to buy SE, but at this point even a venture capital firm would probably know what to do with their IPs better than current SE management.
They could be streamlining for a sale. Or they could be offloading studios that made unprofitable games because they couldn't adequately manage them. It could even be both.
Square-Enix has never been afraid of offloading their Western studios if they were losing money. Just look at IOI. And look at how IOI turned things around once they were in control of their own destiny. I do think it's good of S-E to be agreeable in terms of selling off their IP and studios like this, as there are a lot of big publishers who would - out of sheer spite it seems - grind the IP and the studios into dust before they'd even countenance selling them. Probably as some sort of face-saving exercise should the liberated studio and IP thrive away from the mothership and make them look incompetent.
At the same time, depending on who any potential S-E buyer is, the Western IP may not be attractive to them. There could be overlap between IP the buyer already owns (as such, they don't want to pay for it) or the buyer felt the studios that come with said IP don't really fit into their structure (i.e. they may have a studio nearby that could lead to overlap, causing costly redundancies and bad PR, or they can't adequately support the studios for reasons xyz which could lead to costly redundancies and bad PR).
Another consideration is the S-E Western studios could be bogged down by third party deals such as the Marvel deals that Square-Enix signed, or the Perfect Dark co-development deal with Microsoft Studios that Crystal Dynamics currently has. These deals may not fit into the roadmap of the buyer, and supporting them may prove too much of a distraction, be a direct conflict of interest, or prove overly beneficial to their competitors.
Again, it all depends on who, if anyone, is looking to buy Square-Enix. The rumours say Sony, and if so then most of the above applies. They obviously don't want one of their studios developing first party Xbox games, and Tomb Raider is a waste for Sony when they're going large on Uncharted. And while they're not averse to making Marvel games, Sony is definitely more keen on developing their own IP than licensing other people's IP (Spider-Man is in a unique position, when you look at the film rights), so I don't think having GOTG or Avengers really interests them.
About the only major property from the Embracer deal thusfar which we know Sony might like is Deus Ex, because they really don't have anything quite like it, but even that's a mismanaged series currently on terminal decline thanks to S-E's negligence. Maybe Sony doesn't see value or potential in releasing a new game in the series and indicated to S-E that it should be offloaded before they sign on the dotted line.
Embracer, on the other hand, seem to want to pick up any shit that's going. They're pretty much a dumping ground for anyone who has a studio or IP to sell at this point. I don't know how they're paying to keep all these studios afloat and it looks to me like a bit of a house of cards, but whatever they're doing is still working well for them since they haven't gone under yet.