I think I'm responsible for a sham of a M/M marriage.

Back in March I set up my best friend (B) with an old acquaintance(S), I thought that they'd be well suited for one another. After about two weeks of them knowing each other B tells me that while S was a nice guy he was only continuing to see him because it made X (who B really wanted) pay him more attention. Despite the fact that S has been working on B's house and buying things with his own money, he planned to continue to see S until jealousy caused X to commit to something. After years of knowing each other I was shocked and dismayed at B who I'd learned over the years was far more selfish and shallow than I would ever have believed in the first couple of years, had reached a new low. S was texting me about how enamored with B he was (He's a serial monogamist having had one ten year relationship and one 15 year relationship, and was desperate to jump into another relationship). I considered telling S about B's true motives, but couldn't bring myself to.Literally the next day B, who only recently started driving (in his 30s) pulls out in front of oncoming traffic. he totals his car, but is unharmed. He calls S, who a week before had a tumor removed from his brain, to drive the 50 miles from his home to take B home from the hospital, which is less than a mile from B's house. S begs brother for his car keys (he was not to drive for two weeks after the surgery.) I get a call about the accident late that evening from B who briefly tells me about the accident, and that S, who I knew was not to be driving was there.B makes no attempt to look into a new car, S does all the legwork at a dealership 50 miles away, then literally goes and gets B to sign the contracts on the new car.Less than a month later I get a message from S, saying that he thinks he's gonna do something crazy. I, knowing his desperation to be in another committed relationship simply reply "You're going to propose..." he answers in the affirmative and three days later B accepts the proposal, they decide to get married mid July, after the SCOTUS decision, then have a reception at B's home afterwards.B calls me to tell me that the ceremony is going to be a small, private one and tells me that they'd like me to be the witness since I introduced them. I tell B that he knows I can't do that because being around couples makes me suicidally depressed. The tone in B's voice tells me that he was expecting this answer. I take the opportunity to ask B what happened that he's suddenly wanting to marry someone that was too old and unattractive for him a month before. He makes a well rehearsed souding excuse about falling in love with S while they were on the way to pick up his new car. I know it had to be apparent that I wasn't buying it. This is the last time B and I have spoken on the phone. SCOTUS came back with the go for marriage on Friday and I get a [mass] email from S saying that they've moved their wedding up to July 2nd. Reception will still be on the original date.Today, the day of the wedding, I get a call from a mutual friend of B and me, telling me the wedding pictures were up on Facebook, and I needed to look at B in them.B has these fake smiles that I always point out to him as being his "mechanical smiles" the only genuine expression on B's face in the pictures from the ceremony are while joking with his former roommate (who he messed around with and had feelings for) Everything with S, or the group is a mechanical smile, obvious to any of us who really know him. S looks elated.B and I were really close, close enough to know each other's finances, B had already consolidated credit cards last year, then got more cards and maxed them out, then the week before meeting S took out an equity loan to do unnecessary work on his home that essentially left him with VERY little to live on.I feel like B who I thought I knew has Married S after knowing him for less than four months for the income and free labor, exactly the same thing that I've spent my entire adult life fearing would happen to me.