The pronoun "es" in the expression "wie es der Zufall so will"

Question

Wie es der Zufall so will, wechselte auch schon Maxwell selbst von den Katalanen nach Paris.

I wonder if "es" in the expression "wie es der Zufall so will" is the placeholder subject for "der Zufall" or the direct object?

Answer 1

The verb »wollen« (to want) needs a subject that tells us who wants something, and it needs a second completion (»Ergänzung« in German), that tells us what is wanted by the subject. This is true for both languages, German and English.

Those sentences are grammatically incomplete, you can only use them as ellipsis if the thing that is wanted is known from the context:

Ich will.
I want.

In German, this completion can appear in various forms, but it has to be there. I don't want to grammatically describe all those possibilities, I just want to show some of them:

Ich will schlafen. = I want to sleep.
Ich will fort. = I want to go away.
Ich will ein Auto. = I want a car.
Ich will, dass du mir vertraust. = I want that you trust me.

In your sentence we have »der Zufall« (the luck, the fortune) as subject who wants something, and like in my last example, you can write what it wants in a sub clause, beginning with the subordinate conjunction »dass«:

Der Zufall will, dass auch schon Maxwell selbst von den Katalanen nach Paris wechselte.

(Note, that the verb in a subordinate clause has to stand at the end.)

Now you can add the pronoun »es« to the main clause:

Der Zufall will es, dass auch schon Maxwell selbst von den Katalanen nach Paris wechselte.

This is an option, that you also can find in other sentences:

Stimmt, dass du bei Ilse warst? = Stimmt es, dass du bei Ilse warst?
Ich mag, wenn du mich küsst. = Ich mag es, wenn du mich küsst.

In all those construction »es« is a placeholder for the complete sub clause that comes immediately after it. This turns the sentence before the comma into a complete main clause that could stand alone without its sub clause:

Der Zufall will es.
Stimmt es?
Ich mag es.

So in the sentences that contain both, »es« and the sub clause, the sub clause is no longer a completion of the verb in the main clause. (Without »es« the sub clause is a completion of the verb.)

And now you can modify the main clause:

Der Zufall will es. = Fortune wants it.
Wie der Zufall es will. = Wie es der Zufall will. = As fortune wants it.

But now, in German you have to put the verb to the end of the sentence, because it no longer is a main clause. What was the main clause before, has now become a subordinate clause that needs to be added to a main clause:

Wie es der Zufall so will, wechselte auch schon Maxwell selbst von den Katalanen nach Paris.

And now, the part marked bold is a completion of the main clauses verb wechselte. So the complete sub clause »Wie es der Zufall so will« occupies position 1 of the main clause, having the verb of the main clause sitting in position 2, as in every German statement-sentence.

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extra note:

When talking about German grammar, please forget the terms "direct object" and "indirect object". Those terms maybe are useful in languages like English, but those terms are not defined in German grammar. German has genitive, dative and accusative objects, also predicative objects and even sub clauses that can be objects (although you no longer call them Objekte but Ergänzungen = complements, completions).

When you learn German in school as a German native speaker child in Germany, Austria or Switzerland, you never ever will hear the terms »direktes Objekt« or »indirektes Objekt«.

This has been discussed here: Was sind direkte und indirekte Objekte? (in German language)

Answer 2

It's a normal object. German has somewhat involved rules about where nominal and pronominal subjects and objects have to go, but there's a lot more freedom than in English. This sentence is perfectly idiomatical.