In a war there may be a Right and Wrong side - and there may also (and separately) be one side with a Right cause, and the other whose cause is Wrong.
I am therefore using Good and Evil to refer to the nature of a society's values; and Right and Wrong to refer to the specific causes of a war.
Good/ Evil and Right/ Wrong are separate issues.
Even when one side is believed to be in-the-Wrong, both sides may still be Good; in that both of the sides are - overall - fighting for Good values.
Thus: I am distinguishing specific causes and general values. The cause of a specific war may be Right or Wrong; the participants in a war may be Good or Evil.
In considering many wars of the past, we often feel that both sides were basically Good - regardless of the specific cause for which they were fighting.
Perhaps the Trojan War is an example - in that people often regard both Greeks and Trojans as essentially Good societies - whatever the rights and wrongs of the cause of their war.
Athenians and Spartans are probably another instance; both societies are admirable (Good) in different ways - aside from the causes of their wars.
In other wars we feel the opposite: both societies engaged in a war are basically evil, whatever the specifically causal "Rights and Wrongs" of that war may be.
It seems that there can be any combination of Right/ Wrong, Good/ Evil in particular wars.
At one extreme; a Good society might engage in a Wrong war with an Evil Society. So one side is Good and Wrong, the other side is Evil and Right.
In such a situation; the tendency is for us to support the side we regard as Good - because we want the Good society to win. The temptation is then either to ignore, or to lie about, the causes of that war.
Or, at the other extreme, we may wish for the side we regard as Evil to be defeated; even when they are actually 'in the Right' in terms of this specific war.
For many people this may be something-like how they regard the Second World War - specifically against the Third Reich. Because the National Socialists are regarded as the Evil side and people want them defeated.
Therefore people are not really interested in whether the specific cause of the various Western Allies declarations of war were honest or coherent (which is at least doubtful).
Similarly with the entry of the USA into the WWII: people are not really interested by the provocations and engineering that went into the decision to declare war; because they believe the war was against Evil societies (at least; Germany and Japan are/were regarded as Evil societies - Italy... not really).
Even if the Western Allies can be shown to have been in the wrong about the specific causes of war; judgment of Good and Evil 'trumps' such considerations.
Good/ Evil is primary - Right/Wrong very much secondary.
When it is not obvious to posterity that either of the side was Evil; then the question of causation becomes much more relevant in choosing which side 'ought to win'.
This is more the case for WWI. Nowadays, people find it hard to believe that there was much to choose between the two sides of 1914-18 in terms of Goodness or Evil.
Consequently, the war seems difficult to justify in terms of values - and the specifics of Right and Wrong take a larger place: e.g. who was the aggressor?
Yet, even if causality is established clearly; in the absence of an asymmetry of values; such considerations seem relatively trivial - and are often regarded as mere propaganda and name-calling.
My conclusion is that it is as well to be honest with oneself about such matters.
When we regard a war as between a side that is basically-Good in terms of its values; and another that we regard as basically-Evil - then we are not really interested in the specific Rights and Wrongs of how it got-going, or what sustains it.
We just want the Good side to triumph - and to do so without itself becoming Evil.