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I guess I shouldn’t have that expectation. Perhaps it’s because on Earth we see nearby objects aligning with each other because they have been shaped by similar forces, or because they influence each other. But perhaps galaxies don’t interact with each other enough to result in any kind of alignment.

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Molecules of nitrogen and oxygen both have a distinguished axis (along the bond), but because they're gaseous there's no reason to expect them to align throughout the atmosphere.

So too with galaxies---which, from a cosmological perspective, are essentially infinitesimal dust.

The planets in our solar system all orbit on the same plane because they all formed from the same dust cloud that was rotating in the same plane.

Indeed. And to elaborate: the random collisions which flattened the solar system (or galaxy) over billions of years all conserved angular momentum.

Minute Physics have a nice video on this: https://youtube.com/watch?v=tmNXKqeUtJM

Nice video, thanks for sharing.

And just to clarify to GP, the original dust was not in the same plane and the video explains why it ends up in the same plane.

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