As played, the river is a snap call. In less the BB is a total maniac, the call you made preflop is a total spew. You have raised UTG and were called. This is not a really good spot for a squeeze from the BB, indicating that his range should be very narrow. Typically if you call this raise in this position preflop, you will also almost surely bring the CO in too, leaving you in a difficult position after the flop. In my opinion, given your position, this hand should be folded preflop a very high percentage of the time.

Hmm first of all I would start to detach ourselves from the absolute value of our hand and rather focus on the relative value. (I found it as a clear call with a flush, but after a while I was like wait what?)

Then I would start asking myself questions: what my opponent could call on the turn and bluff the river with? Is it enough compared with number of value hands which he might hold?
Since he called with one player behind he has either pair+ or draw.
So on the river he mostly has at least one pair (rarely T9s). I doubt that he would turn his pairs against your uncapped range into a bluff.

Is he valuebetting something worse than T-high flush?
(My answer is that in case he is not a fish/volatile player then not)

To summarize it, he barely has some bluffs and very rarely bets for value worse hand than ours - I would fold the river. And probably bet around 1/2-2/3 of the pot - our line really looks pretty strong.

I would even fold to a squeeze preflop (maybe 150bb deep it is okay) rather call some pocket pairs or lower suited connectors.

Agree the fold preflop. The CO probably will get odds to call after you and you will be play OOP vs the CO and can be dominated with the FD.
In the river I think the population dont bluff here and you can fold the river with T high flush.
Im not sure about the turn as well. This flop hit the BB range and vs two opponent we dont have enough fold equity.
What you think about the lead ?

Tell me why are the lower suited connectors are better than 78/98/9T? What's the crucial factor about it?

The playabilty of low connectors in 3bet pots such as 76s-54s is slightly better in terms of maximizing our value when we hit. Generally speaking on a flop like 65x villain does not expect as many 65s as he does the T9s on a T9x flop. I just think he is more cautious and preservative.
In terms of balance it is also nice to not be a total outsider on a low boards.
Last but not least, we might run into a set - he more likely has some TT-88, than 77-44.
I mean it is not a huge difference at all, but it is something and poker is all about those small ball things if we understand the general strategy.