I already pointed to both Saurfang and Baine as to why doing nothing isn't an excuse, the “there was none” is for the majority of the horde who stuck with her until she left them which includes the whole of the forsaken council -Calia.
He didn’t, the devs have said in a QnA years ago that the only people who supported Garrosh was young glory hungry orcs, the dragon maw clan and the black fuse company.Garrosh had popular vote also and also had control of most of the horde.
The cows trolls forsaken blood elfs and older orcs were all against him from the moment he became war chief as shown in the shattering, cata questing, tides of war, and mop questing where they all break off leading into SoO.
Ya and all of that is horrible writing.As for the forsaken, they're gonna look after their own and they need leadership. Renouncing sylvanas and regretting their part, along with sending troops to defend Amirdrassil is gonna have to be enough. So the alliance needs to suck it up and accept it without causing another useless war because they're still upset at a lack of justice against some forsaken.
The Forsaken can find new leader ship without letting abunch of Sylvanas’s core staff take up the roles as seen by Calia and to a lesser extent Voss.
Pretending they regret any thing while giving all those involved -Sylvanas a free pass is a farce.
And no one in there right mind would let them send troops instead of turning them away and telling the horde to send the Earthen ring or other members who didn’t take part in BFA.