moon craters; why all moon craters looks like 90 degrees impacts ?

i was going to make a really dumb guess about that, but i always like to google stuff i'm not sure about, and turns out there's an explanation posted for this right there for you

https://www.scienceabc.com/nature/universe/why-are...

"Short answer: When a meteor hits the lunar surface, a shockwave spreads out in all directions and the impact creates a dent in the surface that is much bigger than the size of the impacting object itself. Since the impact sprays ejecta in all directions in equal proportions (just like the shockwave of an explosion), the direction and incident angle of the impact become irrelevant in determining the shape of the crater."

Not all, many are oval indicating an impact at an angle.

Because there was no Atmosphere to slow or deflect them

Speed.  High impact velocities create a more uniform shock wave, and angle has less affect. Slower impacts have less energy to absorb, and the impact angle will have more affect. 

See link for a lengthy answer to this, in short the impact creates an explosion, explosions "go out" equally in all directions.

https://www.scientificamerican.com/article/why-are...

Any impact at greater than 25-30 degrees generally creates an approximately circular crater. However, if you look closely you will see there are reasonable numbers of craters clearly resulting from glancing impacts. Part of your confusion may be from secondary craters--ejecta from an impact thrown miles away and coming down to form another crater. These are almost invariably circular.

There is no atmosphere on the moon to divert any impact on its craters.That is why.

You have not seen enough craters--there are plenty of egg shapes, avocado shapes, even a few zucchini ones. Google search for those. Those are from low angle ones.