Why is earth on an axial tilt of 23.4 degrees? What were the influences for this to occur? Did some things play a bigger part that others?
 A: An impact, possibly the same impact that caused material from earth to fly off to space and create the moon, tilted the earth to $23.5^o$
A: I thought the tilt was caused by the formation of the earth.  
When the earth formed from the gas of the pre-solar system, the gasses rotated and created a disk with an axis of near 23 degrees.  When the disk got dense enough, it condensed it to spheroid we know know and love, keeping its tilt from its gassy days.
Taking into consideration a collision that generated the moon, the collision could certainly have nudged the earth's tilt to the 23.5 degrees we know today.
A: It's not constant, so there is no magic about it.  It varies within a range, reflecting stabilising interactions with the moon and the sun, and the equatorial bulge.
A: This would be better in astronomy since the earth collided with another planet size rock and the moon was the result. Since the center of the earth is fluid, the tilt of the axis would vary considerable, but the moon has a stabilizing effect.
