So i guess there are few sets of options we can propose here:
1)Karl Lind caused the global wipeout
2)Karl Lind survived the global wipeout
A)Karl Lind stayed in the destroyed world and became god of reborn fantasyland
B)Karl Lind skedaddled to alternate universe in the middle of mayhem and became god of it
I)MC is his distant descendant
II)MC is his unknowing reincarnation
III)MC is a vessel cultivated to harbor Karl's soul
My personal bet is on 2BII
I personally vouch