It's not so much that pi is infinite, meaning that it has infinite decimal places, but that it cannot be expressed as a fraction. For example, the fraction 1/3 also has infinite decimal places when expressed as a decimal (base 10) but it can quite obviously be expressed as a finite fraction.

Nobody 'got' pi to be any particular number; it is the natural ratio between the diameter of a circle and its circumference, and by virtue of that, it is also the ratio between the square of a circle's radius and its area.

I'm sure a quick Google will tell you to how many digits pi has currently been calculated.