I was asked how is it possible that so many Czech people don't belong to any of the churches. What caused current situation when almost 70 percent of whole Czech population isn't registered in any of the existing churches? Why are so many people in the Czech Republic atheists? I'll try to answer these questions.
We have to start deep in the past. We can say it all started in the beginning of 15th century. Most of you probably already heard about Hussite wars and their reason - disagreement with the catholic church, which had many flaws those days. New movements and church which appeared from the Hussite Wars, so called Hussites or "Chalice People", was really strong - almost 80 percent of Czech population belonged to them before the 30 years war.
Catholic church was percieved as a rich, but hostile, selfish organisation. And this was valid even during the 30 years war. But after the Czechs lost their fight for new king (they wanted another king, not one from Habsburg family, but this is looong story), recatholisation started. It means situation when common people are given only one chance - to change their faith from protestant/hussite to catholic. Noblemen were given more chances, they could leave the country which was not allowed to common people (but it happened anyway and many Czech people left to other European countries because they were not willing to change their faith).
Stone cross from the beginning of 19th century near Zbožice, Vysočina region.
Then we have about one and half century when only Catholic church was allowed in Czech lands. Josef II.'s law from 1781, Patent of Toleration, showed that many people were hidden protestants - many people, whole villages in some areas such as Vysočina region, declared themselves protestant in very short time after the Patent. But the numbers were low, just about 5 to 10 percent of the population (low number compared to those 80 percent of non-catholics before the 30 years war).
The rest of population remain catholic. And here the problem rised. When Czech nation began its way to the modern nation in the second half of 19th century, Catholic church was still percieved as something foreign, German and hostile to Czechs (as it was during the Hussite wars and 30 years war and the years after it). Hussite period was percieved as a golden age of Czech nation - and Catholic church was losing worshippers.
And this continued after the breakdown of Habsburg monarchy. People were allowed to leave a church from 1872 but not too many of them did it before 1920 - the pressure from the church was still quite large because people meant money. But since 1920 the number of believers has declining tendency. People were leaving Catholic church by thousands as they still percieved it as a hostile organisation. Many people declared themselves "without confession" (bez vyznání) or belonging to new Czechoslovak (Hussite) church. And many people of the elites (such as first Czech president Tomáš Garrique Masaryk) were presenting this tendency.
And then - the Second World War and then Communism came. And communism wasn't regime friendly to religion. The percieving of Catholic church as something hostile was maintained by the communists because church was still quite strong in 1940's and 1950's. Communist propaganda against church was strong, really strong. Physical repression, liquidation of church orders, political show trials with prelates and priests... But all this had no chance to success if there wasn't that historical background.
All this led to the current Czech situation when almost 70 percent of people are "without confession"...