State atheism isn't "it's illegal to be a theist," it means that the state is explicitly atheistic in its law, not just secular (indifferent to theism/atheism), but that people in government, or at least anyone in a very high position of power, actually have to be atheists. You can still be free to believe whatever you want, but just don't run for public office if you are detached from reality. Countries like this often have historically even provided funding and support for things like religious institutions like churches for people to freely worship, but since it is done by atheists, the motives are slightly different: it is there to help contain the religiosity, not to spread it, so things like evangelism in banned. If you come to religion on your own free will without indoctrination or evangelism, then there still is a place for you, but neither that place or yourself can then use that as a basis to evangelize.