Why is Mars similar to Earth?
Both have solid, rocky surfaces, an atmosphere and water. However, Mars has a very much thinner atmosphere, almost no free oxygen, and most of the water is frozen.
The length of a day on both planets is around 24 Earth hours (Mars 24.62 hours) even though Mars is only about half the size of Earth.
Because Mars has no oceans, the available land surface there (practically all of the surface) is about the same as the dry-land surface on Earth.
No, Mars is much smaller than Earth, but both planets have similar amount of dry land. The diameter of Mars is half that of the Earth. Mars has ten percent of the mass that the earth has. The whole surface of mars is about equal to the all of the dry land surface of the Earth. Mars has about one third the gravity of the Earth.
Mars and Earth share a similar angle of axial tilt - Mars, at present, has a tilt of 25 degrees, and Earth maintains a fairly constant tilt of 23.5 degrees. However, Mars does not maintain a consistent axial tilt over millions of years, so it is purely coincidence that Mars' current axial tilt is similar to Earth.