Maybe at the same time that socialism has grown, people have become more able to think for themselves
That is unlikely as that is the exact opposite of what socialism is about. Socialism is about the hive mind. Everyone is equal and the same. There is no individual in socialism. It is all about the collective. All should be rewarded equally and all should suckle from the ghastly teat of the state. The state is at the top, and everyone else is underneath it, boot on face. Individual thought is discouraged. Today we call it hate crime or politically incorrect, to express thoughts outside of the collective. It is actively discouraged wherever it occurs.
It was pretty difficult for Victorian Britons to find books on Buddhism or meditation, let alone join a group to practice it. Christianity was basically the only game in town - which I suppose was good for those like Rowbotham, who felt their ego threatened by anything which undermined it as "the one true faith". Though I suppose many of those he was arguing against were Christians too.
Victorian Britons had this thing called Queen Victoria and she had far more power than our modern Queen. Promoting divine right was still important. It was the Queen's British Empire, she was ruler of the most of earth. Maintaining Christianity at the time was still an important requirement. I would point to the Suez Canal incident, and Breton-woods as important turning points ... those signalled the end of the British Empire and really the last gasp of the church's power over Westerners. The US government (the new rulers of the world) were a democracy without monarchy and had no need of God.
You are not correct in the turning points of the empire.
The First World War hastened the break up of the empire and some of our largest colonies were moving to independence. WWII saw the UK crippled by debt, and unable to afford the empire, and as a consequence of WWII a large number of colonies were actively seeking independence shortly afterwards, think India, and Far East as well as African countries.
All of that was before the Suez Crises.
Queen Victoria had no more political power than any other modern day monarch, but she may have had mor epublic opinion and influence. Not the same as power.
However the decline in attending organised religious events can be correlated to the level of impartial education, i.e. education that is not reinforced by religious doctrine, but by science and learning, allowing the pupil to make their own ideas.
The countries where stigma, convention, peer pressure, or laws requiring adherence to religious practices are those countries where religion is the highest (i include the USA in that bunch) and this potentially restricts free thinkers.
Socialism certainly tried to suppress religions, but for the UK, we never ended up with a socialist state, so i cannot agree with your point that it was socialism that created a hive mind, and that everyone in the UK is equal and the same. That is clearly false.
However what is interesting, and touched upon in another thread is that the numbers of FE supporters in countries that are free (by either social or government pressures) to believe in whatever they wish, appears to be much lower by capita than countries that are considered more religious.
Take the FE convention in the UK, very very low attendance per capita and probably much lower per capita head than ones in the states, even considering the relatively smaller distances involved inn the UK.
I would suggest therefore that there is a link between Christianity, and faith in what is written in the bible and blindly following it, and the numbers of FE supporters.
I content that those truly free thinkers, free from religious pressure, (If they wish) and free to research and choose what they believe are NOT FE supporters. How could they be?
I contrast, most of the FE supporters look upon Rowbotham as a sort of prophet who could do no wrong and who discovered the flat earth, and blindly follow the teaching of him, as they do not contradict the bible, so therefore MUST be correct.
Most of the more recent FE influencers, who “revived”, for want of a better expesssion, the FE movement such as Voliva and Johnson were definitely very much bible fanatics, who saw no other reason to read any other text books!