1) Here is what one of Israel's leading Holocaust historian has to say about it:

Ahren 2015' Yehuda Bauer, Israel’s preeminent Holocaust scholar, is a prominent case in point. “After the war, they caught him (Wisliceny) and tried him at Nuremberg, where he tried to eschew all responsibility, saying: ‘It wasn’t Hitler, it wasn’t me, it was the mufti,' . . It’s clear that his account is untrue: the Germans had started annihilating the Jews half a year before Hitler and the mufti met.”

2) Eichmann was Wisliceny superior. Eichmann denied the Mufti's involvment during his trial. Here is the source:

Hopwood 1980, p. 69.'During his trial in Jerusalem in 1961, Eichmann denied having known the Mufti well, affirming he had met him only once during an official reception. The evidence for the friendship came from Dieter Wisliceny, one of Eichmann's aides, who months before the Nuremberg trials had begun to prepare an alibi for himself at the expense of Eichmann. Wisliceny went much further and accused the Mufti of being an "initiator" of the extermination policy. Other evidence of the Mufti's alleged role came from Rudolf Kastner (a Jewish leader in Hungary), who reported that Wisliceny had told him that "According to my opinion, the Grand Mufti . .played a role in the decision . . . to exterminate the European Jews . . .I heard say that, accompanied by Eichmann, he has visited incognito the gas chamber at Auschwitz". These reports coming only from Wisliceny must be questioned until substantiated from other sources.'

I won't argue any further with you because it's quite clear that your desire for this to be true is much stronger than your faith in historical sources. I'm sorry to break it to you, but sometimes countries fabricate stories to help their propaganda efforts. All countries do this, including Israel. This "Mufti" story is a fabrication.