I'll bite. After all, you took the time to go in old posts of mine done in different threads.
I was against World Cup going in Qatar for several reasons: a) it was bought by corrupting people; b) it was build by foreign workers who were working on unsafe conditions; c) there were concerns about the treatment of women and LGBTQ+ community.
As far as I can tell, neither of these 3 things are problematic with the United bid. They are not corrupting anyone, instead are being the highest bidding. If they build a new stadium, it will be build by respecting safety laws in England. And the women and LGBTQ+ United followers have nothing to fear. They mentioned investing in the United's women's squad and in PSG, they even played with rainbow shirts.
While both getting the World Cup and buying United are sportwashing projects (and even more important, putting Qatar in the map and in good terms with Western powers if a larger conflict with Saudi Arabia and/or UAE happens), when it comes to rights of marginalized groups, it actually had benefits for them. Women in Qatar, for example, are not required to wear hijabs anymore, they outnumber men in universities, and the divorce rate is up (for better or worse). While LGBTQ+ community in Qatar is obviously massively discriminated and it is illegal to be gay in Qatar, there were some tiny encouraging steps in this direction too. For example, gay couples were allowed in Qatar, they could book the same room in hotels etc. Far from what we want to see, but remember that it is a culture that 70 years ago were beduins and is pretty much unanimous in opposition of gay rights. But yes, eventually it will get there, and the more interconnections with Western culture, the faster these rights will come.
Now, I won't lie for a single moment and say that this is my primary reason for wanting them at United (to make Qatar a better place). Nope. My main reason, is as you might have guessed, money. United lost around 1-1.5B in the last 17 years as privilege of being owned by Glazers, in paying debt, interest, dividends and commission. Money that if spent on the club would have allowed United to be debt free (or near debt free), and have a new state-of-the-art stadium. Instead, we have an aged stadium, 600M in debt, 300M in transfer debt, and almost no cash reserves. Just clearing the debt and getting a new stadium will cost 2.5B, if not more. At the same time, we have other state agents (City and Newcastle) who are being backed by outside money. It is simply impossible to compete with them, while building a new stadium. In fact, it is more likely that we will need a new debt just to operate, let alone get a new stadium.
Ideally, I would have liked us to be bought by Apple or Amazon, but it ain't happening. The choices are between Qatar, Jim Radcliffe and some American consortium (with Elliot backing). We can exclude Americans as desirable for obvious reasons. Radcliffe is buying the club with debt (albeit it will be put on INEOS), and it is not planning to do a full takeover, so it won't invest much (any) of its own money at United (you simply do not put money in a business you do not fully own, by owning only 70% of United, every pounds INEOS invests at United, 30c penny go to other shareholders of United). They also are not going to clear the debt. On the other hand, Qatar is clearing the debt, not buying the club with debt, and doing a full takeover so probably they will invest their money to build a stadium etc.
Finally, United is my escapism from real-world problems. I want to see United being the best club in the world, not competing for the sixth place, while oil-backed clubs win trophies every year. After a decade of winning only 'moral trophies', I want to see us winning the real ones again. And I think that it is very unlikely for this to happen regularly (one-offs like Leicester are obviously possible) without a sugar daddy. Not unless some law really prevents City and Newcastle owners to put their own money in the club. And after 15 years of waiting for such a law to be enforced, it is foolish to believe that it will happen in the next 15.