Tape - It takes up space. Space is what you need to get the beads into the middle to give you some extra slack to drag the last bit of bead over the rim.
This.
I sometimes put two layer, even three layers of tubeless rims tape if the tyres is too loose on the rims when converting it into tubeless to reduce chance of air escaping while inflating.
I think mine is 2 wraps. Can't remember who's directions I was following but I could inflate it, without tyre jizz, using one hand on a track pump and the other on the tyre. Skillz. It remains unridden :(
This.
I sometimes put two layer, even three layers of tubeless rims tape if the tyres is too loose on the rims when converting it into tubeless to reduce chance of air escaping while inflating.