2 Answers

Doesn't surprise me. Many state constitutions were written in an era when to admit one was an atheist may have gotten you shunned or even evicted from a state. I very highly doubt the law would  be enforced today by any of those states. Until someone calls for the removal of the law, it will stay right there in the state's constitution because it's a long and lengthy and expensive process to get a law removed from a constitution. If any state decided to enforce the law, they would be sued and they would lose because according to the US Constitution it is written that there can be no religious test for public office. It's really only by choice that any politician says what religious denomination he/she follows, if any. Religion is good for voting points. Many in office claim to be Christian but they certainly do not act like it but Christianity sells so, it's good for the votes. 

If a Muslim gained US citizenship, he could run for public office. Even if such a law as above could be enforced, a Muslim is an adherent of Islam. He would meet the criteria. Obama has many Muslims in his administration.