The two prongs/forks/sticky-out bits are supposed to swivel, for the reasons you said.
Just make sure that you have the bracket screwed into the wall properly. 4 screws??
I mean
really screwed in. I'm worried because you've cracked it already, make sure it's not going to come off.
If it's a wood frame and plasterboard wall, make sure you are into the stud (the 2x4 underneath). If it's brick, use good strong screws and plugs.
I just say because a rather inept-in-DIY guitarist friend just screwed into the plasterboard, no plugs, nothing, I don't know how he managed it to be honest.
He installed his pride and joy Les Paul over his other pride and joy tropical fish tank.
He came home one day to a very wet lounge room, expensive dead fish, glass everywhere and a slightly damp but otherwise unscathed Gibson.
