That's not a massive overbet. The SB only has 8BB. There is no other play for them. Especially OOP!
If they limp, they will miss the flop completely 2/3 of the time. Being OOP, if they bluff lead, they will get called when they are beat. Conversely, they will not make money when they hit the flop if the BB doesn't hit as well.
If the SB raises say 3BB, they are pot committed. In another post I showed that if the smaller stack is less than 5*Raise, then you have odds
to call if you are re-raised. So it is better to shove to maximize FE. In this case 5*3BB=15BB, so an all-in is the only sensible action.
Of course the BB calls here with AK regardless of their stack as the percentages show(a few posts above). The only time the BB may fold is if they are hopelessly short and trying to sneak in the money and the bubble is close.