Your entire theme on natural etc is BB.
Secularism grows like oppressed small bushes under bigger trees of big religions and their sucking water of freedom and venting oppression.
eg. Islam is called religion of peace but there is no peace in any muslim country, all Muslim want to flee from them to countries where there is peace.
Entire population of Indian hindus want to flee from shackles of hinduism and want to breath freedom air.
Both islam and hinduism have so many Gods. Hisuism have many clay Gods like goods, muslim have many Gods like Peers, fageers, mullahs, Imams, saint graves, Awlias and many more. Both hindus and muslim are there by birth chance and not by living choice.
Christianity is already eroded and disappearing from society except for a church hour on sunday for seniors only. Even many churches are now owned by hindus and muslims to run donation business. Investment.
There is no natural dogma etc for creation of secularism, its just oppression, resources, freedom, safety, talent, ecoomics and desire of good life..
Ultimately all religion will die on earth and only existance will matter. Religions will be history and only knowledge of a super energy, Creator, God, ALLAH, Bhagwaan will remain.