Everyone's entitled to an opinion but its a pretty absurd one. Imagine being a director of football or whatever Wards title is and going 'Shit we're 8 points off 3rd place after 14 games, with a game in hand, and still in every competition....best hand my notice in'. Its ridiculous. As is thinking FSG would be triggered to sell because they dont want to fund a rebuild, considering the 'rebuild' is more like signing two or three players. There's clearly far bigger things going on, whether they've just decided its a good time to sell, whether they're all collectively sick at the sportswashing (or have had their heads turned by the prospect of selling to one), whether they're wanting to buy an NBA or NFL team and can't realistically 'afford' both.
It's bigger picture stuff and a combination of factors. They'll have come to realise that longer term, they can't compete with the spending of Man City, and now Newcastle. It we say Man CIty and Newcastle are now nailed on top 4, then the rest are fighting over 2 places and there is far more chance of missing out. Multiple years out of the CL, and funding the club would become very difficult for FSG.
They have probably got the club to the highest value they can. There is no way FSG can sweat the asset any more than they have whilst also properly taking care of the squad. The only way is down in terms of valuation under FSG. Especially if they start missing out on CL qualification (see above).
It's also reasonable to expect that they are far more interested in US sports, than football. From an interest point of view, they simply know and like Basketball and Baseball more. Crucially, US sport also have a modicum of control over spending, which we know they favour.
And let's be honest, the PL is heading for meltdown. If I was FSG, I'd probably also be looking to sell. I don't trust the PL or the FA as far as I could throw them. They have lost control.