Comment ça se fait que v comment cela se fait que?

Question

Are either of these forms strictly correct, or is comment se fait-il que the more orthodox.  A bit confused.

Answer

Bonjour Jennifer !

You wouldn't say "Comment cela se fait que" because "cela" is actually more elegant, "higher standard" than "ça".
Therefore, when you choose to use "cela" you will also use the more elegant question form that is the inverted form in French:
"Comment cela se fait-il que ?"
And in the elegant form, you can also choose to drop "cela" altogether, as it's repeated with "il":
"Comment se fait-il que ?"

I hope that's helpful!
À bientôt !