The concept of Pi and the irrationality of sqrt(2) predates the universe itself.
Think about it.
How? Get rid of the universe, and the concept of pi doesn't exist. Pi is the ratio of a circle's circumference to it's diameter. Circles didn't exist before the universe, thus no pi. There could be another universe where circles are impossible due to whatever laws of physics exist, thus no pi.
Circles (perfect ones) are impossible in our universe, too. Circles are abstractions. If we have successfully deduced a conclusion from a set of axioms, wouldn't that deduction hold true in all possible universes?
The mathematical realist position is that these abstract math objects exist independent of an observer.
Ditto with sqrt(2), you need to "sharpen" the triangle made from half an square forever in order to get all the decimals.