For example, the Moon is smaller than Jupiter. But, if the Moon's transit where to happen in front of Jupiter, the Moon would leave Jupiter completely covered. Same thing happens between the Moon and the Earth. So, the Moon, would never look smaller than the Earth, as it's shown in that animation.
Explain why not. The trigonometry is not hard. The Moon is smaller than Earth. I assume you have no problem with the idea that if the two are next to each other this will be obvious. So what if you were looking at it from a position significantly further away than the orbital distance between Earth and Moon. Why wouldn't the Moon appear smaller in front of the Earth under those circumstances?
Earth is 4 times larger than the Moon but this becomes apparent only when both bodies are lined up next to each other ... but if the Moon is in the foreground, the disc will completely cover the Earth...
Whether this is true literally depends on how far away from the Moon you are. If you are on a spacecraft 1.5 million kilometres from the Moon, with the Earth on the far side of the Moon, how big will the Moon be compared to the Earth (that is, with the Earth 1.9 million kilometres away).
...do not forget that Moon is about 400,000 km away and it looks like a small sphere of only about 2 degrees from the moon Earth...
When looked at from the Earth, the Moon is about 0.5 degrees across. When looked at from the Moon, the Earth is about 2 degrees across. But there are places other than the Moon and Earth from which both objects can be seen. Like out in deep space.
...and if you turn away even more (as in the animated gif) Earth will be just like a point , come on!!! It is so difficult to understand?
Apparently it is for you.
Here's a simple illustration:
E----------Mn----------------------------------------You
r
t
h
Imagine you're on one side of the Moon with the Earth on the other side. The distance You-Moon is four times the distance Moon-Earth, and the Earth's diameter is roughly four times that of the Moon.
How much of the Earth is the Moon going to cover?
Answer: Not all of it.