Hmm, thing is that announcement was never from Top Rank. How's he gonna put a gag order on his #1 guy? He cant revoke his twitter account. He cant stop him from calling Amir Khan and saying lets do this, while Khan says, cool Im in. The onus was on Manny to keep his trap shut and introduce whomever those guys were to Top Rank and see if a deal could get done. Manny fucked it up, trying to be a businessman.
AFAIK, the story goes, Manny came up to him (Arum) saying he was contacted direct by some guys in Dubai that offered to pay him $38M to fight Khan there. Arum said "whatever, you and Koncz let me know when/if details materialize, while I work on stuff thats real for your next couple fights." Next thing you know Manny is all over ig and twitter saying he's fighting Khan in Dubai... follow the timeline and you'll see Bob Arum said immediately that announcement was bullshit. The announcement got some traction in the media, (like it did here) and Arum probably tried to reach out and get a deal done for the sake of reputation and those dudes were nowhere to be found. Hence the deal is dead announcement from the man himself...
Not sure how much control one can have over that scenario. Between two adults in business there needs to be an understanding of decorum in how we are gonna proceed in negotiations and in media/public announcements. Im sure Top Rank has their format, and it sounds like Manny got ahead of himself and ignored the TR process.
Cant really blame that on Arum. He cant control the free will of other people, he can only suggest what to do and what not to do.