about pronoun etc.

[ivygreen]

Please teach me why can't "it" use in this sentence below?
And, why "being" is used ? Is it to make a phrase?

"(This or That or Such) being the case, the plan was canceled."

[Soup]

Please teach me why can't "it" [be] use[d]

From your example sentence, the pronouns that and this are part of a bigger phrase. That/this is short for that/this reason, which stands for the clause in blue:

There wasn't enough money, and that/this [reason] being the case, the plan was canceled.

That and this are adjectival; they would modify the noun reason if it were not omitted.

The pronoun it, on the other hand, can't function adjectivally and so it can't be synonymous with that/this; it co-occur with a noun as it does here:

There wasn't enough money, and it [reason] being the case, the plan was canceled.

But! It's incorrect only if we assume that the noun reason has been omitted. Assume otherwise, that it doesn't function adjectivally, that it stands on its own; that it stands for not having enough money, and the sentence stands correct:

There wasn't enough money, and it (= not having enough money) being the case, the plan was canceled.

And, why "being" is used ? Is it to make a phrase?

You're right. Being is a participle, not a verb. If you want to turn a clause into a phrase, make the verb non-finite (make it so the verb has only the one form, not more than one form).

Finite: more than one form
I am
you are
she is

Non-finite: one form only
I being
you being
she being

Phrase: that being the case (non-finite verb)
Clause: that is the case (finite verb)