Welcome to Inward Quest.

I think there's a couple of assumptions underlying your question.

1. In order to become victims (your word), they must have actively believed themselves into that role.

2. Death is a bad thing.

I would like to suggest that both of these assumptions are incorrect.

Incorrect Assumption 1: In order to become victims, they must have actively believed themselves into that role.

In order to become a vibrational match to something unpleasant in your life, it is not necessary to believe anything at all about that particular thing. Just find things in your life to feel bad about and the unpleasant vibrational matches will start physically manifesting. :)

Then get upset about those manifestations, and you'll soon start attracting more and more unpleasant manifestations (both in number and in strength of unpleasantness).

It's just the impersonal Law of Attraction doing what it does...responding to where your thoughts are predominantly focused.

I think where people sometimes get confused is thinking that the Law of Attraction manifests according to subject matter instead of emotion. In fact, your manifestations can come about from unrelated subjects but which create related emotional responses within you.

There is more information on this in Is visualization a key component in the manifesting process? and here is a relevant quote:

This explains why, for example, you can feel consistently frustrated by, say, your boss at work but it manifests as you always getting stuck in supermarket checkout queues (it matches frustration). Or your television suddenly stops working (it matches frustration). Or your car doesn't always start properly (it matches frustration), and so on.

So those victims did not necessarily have any beliefs related to the Nazi Party.

Another common (and more obviously connected) way to attract something you don't want is to "push against" the thing you don't want...for example, either fear it, fight it or constantly try to protect yourself from it.

Because in order to do those things you must again be focused on what you don't want, which again produces the negative emotional reaction which indicates an unwanted manifestation is coming...except in this case, the manifestation is more obviously connected to the thought pattern that gave rise to it.

Incorrect Assumption 2: Death is a bad thing

In the moment of transition (or death), which is a withdrawing of focus from physicality, all resistance and negativity is instantly released because those are only products of being focused on the physical plane.

So the death experience itself (for most generally resistant people) becomes one of joyous release.

Since the Law of Attraction is always matching up vibrations then if, for example, someone is feeling trapped in their life and are actively seeking freedom, it is quite possible for them to be a perfect vibrational match to death, which provides instant freedom and joy...if it is something they are open to.

Before anyone asks, I should point out that if someone has powerful desires still drawing them to the physical plane, then death is an unlikely positive manifestation because it doesn't satisfy those unfulfilled earthly desires

Indeed, Abraham have said (only half-jokingly) that if people truly understood what a joyous event death really is, there would be many throwing themselves off high buildings everywhere :)

Humans have such a messed-up idea of what death really is that these last few paragraphs can sound truly ludicrous at first...which just demonstrates how deeply conditioned so many of us are regarding this subject.

And yet, so many apparent disasters where many are killed together start to make complete sense when you begin to scrutinize the idea closely.

Yes, there will be those who are caught up in those incidents because of fear-related emotions but there will also be many others who are choosing it (at some level) as a quick way of undergoing the death experience.

A general rule of thumb I have come to observe is that if someone's death is fairly instant and they were not predominantly in a bad-feeling place, it is usually because death was a happy vibrational match (the "next logical step", you could say) and it was a positive choice.

On the other hand, if a transition state is long and lingering (such as through some debilitating disease) then the death is resistance-related.