I hear what you're saying, but most of these guys seem to be retired and have their fortunes made. If they were looking to maximize every revenue stream from the club then there's no way they'd have given us an interest free loan for the main stand. That might have cost them money, but it's relatively small beans compared to what they'll make if they sell the club, or, as seems more likely, a large minority share in it.
The point is, they have invested a huge amount into the club, which they could very easily have invested elsewhere for much greater profit. They are wealthy men, but wealthy men never really retire from accumulating wealth, and I assure you that each and every one of them will have multiple ventures currently increasing their personal fortunes by eye-watering figures on a regular basis.
If they were only interested in the club as a money making scheme, it's a really poor choice of investment for experienced hedge fund managers. They could already have made a lot more from what they have put into the club than they would ever be likely to see back, even if they did want to sell all or part of the club.
The appeal of something like Liverpool to FSG has been much discussed here, of course, and the only logical answer appears to be that it is a prestige vehicle for them. Owning Liverpool FC opens doors. It raises their profile (they were previously well known among baseball fans, but they are still relatively small fish in the football world) which in turn leads to further opportunities (not all of them purely financial; want to meet Paul McCartney*? Tell his people you own LFC and chances are you'll get to meet him)
How that translates to actual investment in the club, and the stadium in particular, now becomes a little clearer. The Main Stand expansion has already bought them a huge amount of unique coverage. It benefits the football club and the fanbase, of course, that's vital, but it also demonstrates that they are a group with the means and the will to do something that had previously been considered impossible, and to do that with some style and class. (Gives you something to chat to Sir Paul* about when the meeting is set up.)
There is a law of diminishing returns with this stuff. The best thing FSG can do is get the club winning trophies. In the meantime, they have said that they will under-promise and over-deliver. In terms of the stadium, so far, they have played a blinder. And while the planning application for expanding the Annie Road may not be a "promise" as such, it would reflect poorly on them if they just dropped it for no obvious reason now.
Not aimed at anyone specifically here...
*re "Paul McCartney", I do realise that some people on this site are ear-bleedingly literal about things like this. Sir Paul is just an example here of someone elusive who people might want to meet with some connection to the city. It's not about Paul McCartney the man, the musician, or the bloke who has been impersonating him since Rubber Soul came out. Leave it. Step back. Have a think about it. Think of Chris De Burgh instead if it helps. Or Brad Pitt. Or that Irish fella from the WWE. It doesn't matter. Think about how you'd go about getting a round of golf with Liza Tarbuck if that speaks to you more. Bear in mind it got them in the room with LeBron James already.