How Do Phenyl Groups Stabilize the Intermediate in Cis-Trans Isomerization?

[plexus0208]

Homework Statement

1,2-difluoroethylene has two isomers, cis and trans, and they do not interconvert readily.
However, cis and trans isomers of (C6H5)HC=CH(C6H5) do interconvert (but slowly). How is the
intermediate required for that interconversion stabilized by the phenyl groups?

Homework Equations

The Attempt at a Solution

I think it has something to do with the fact that when a single electron is "delocalized" throughout a large π system consisting of alternating C-C and C=C bonds, it leads to lower energy species... but I still don't get it. What is meant by intermediate? (My professor never really went over this part.)

 

[chemisttree]

If you could convert the double bond to a single bond, you could get rotation about the bond before the double bond reforms. How might you accomplish it?