the expression of “become of” without the subject “what/whatever”

Question

As to the second mode, that of leaving wealth at death for public uses, it may be said that this is only a means for the disposal of wealth, provided a man is content to wait until he is dead before it becomes of much good in the world. Knowledge of the results of legacies bequeathed is not calculated to inspire the brightest hopes of much posthumous good being accomplished. The cases are not few in which the real object sought by the testator is not attained, nor are they few in which his real wishes are thwarted.

before it becomes of much good in the world.

I knew that "become of" expression is used only when the subject is what or whatever. but in this article, the subject of that expression is pronoun "it" Is it possible? and I don't know that that means. And Could I ask you what the pronoun "it" refer to?

Answer 1

"Of much good" in this case means, roughly, "of any use," "of service" or even just "beneficial." Or "useful," for that matter. Break it down, and you'll see what it means:

The man is supposed to wait until his dead
before his wealth becomes
useful ... of much good ... of service ... beneficial ... of any value ...
in [or to, depending on the word or phrase you pick] the world.