Why does 1,3 butadiene have 4 resonance structures and 4 frontier orbitals?

[ssb]

While studying the structure of 1,3 butadiene and considering frontier orbital theory, I came across a graph of the HOMO to LUMO orbitals.

Basically put, when I draw out all the res structures for 1,3 butadiene, i can make 4 of them (i know that 2 of them are very unstable and 1 of them is very very very unstable).

Is there a similarity here or is it just dumb luck that there are 4 of each (4 res structures and 4 alignments in the homo/lumo chart.)

Thanks

 

[ssb]

Also here are some more charts to look at.

 

[ssb]

and the last one (limit of 3 pics per post)

 

[ExistenceGue]

u must have 4 of theme, butadiene formation required interaction of 4 atomic orbitals so sure u must have 4 molecular orbitals that u draw !