Joseph Esherick's The Origins of the Boxer Uprising makes an interesting observation when it comes to assessing the development of religious-political movements: we have a tendency to look at doctrine in isolation. This can lead us to forget that the same ideas can have different effects in different contexts, or to misplace our emphasis on which ideas were important to those interpreting them. Most importantly, 'it is far less important to know where [religious figures] got their ideas than to understand how their ideas attracted an audience.' While Esherick's discussion of the Taiping is relatively brief and is supposed to serve as a point of comparison to the Boxers, it is broadly compelling, so I feel I may as well summarise it here.

The specific theological and Christological doctrines of the Taiping were of relative unimportance to Taiping adherents in and of themselves. While there was strong religious devotion among the Taiping's core adherents, Taiping theology served to underpin a broader set of ideas that were the real appeal to the vast majority of Taiping followers. The central idea revolved around disaster: the Taiping offered a means to survive an ongoing or imminent disaster, and promised a post-disaster utopia. This, Esherick suggests, is partly why the God-Worshipping Society took hold in the Guangxi uplands far more effectively than in the Pearl River Delta: Guangxi communities were much more unstable and thus much less capable of responding constructively to sudden stress, creating appeal for separate, trans-community organisations like the God-Worshipping Society; whereas the more cohesive society in the Pearl River Delta was less fertile ground for such organising.

Why were the Guangxi uplands so conducive to the development of the Taiping? The 'favourable conditions' were, to quote Esherick:

sharply rising population, commercialisation of the economy of the rivers linking the area to Guangdong, epidemics and natural disasters, unemployment from the recently closed silver mines, banditry in the hills and piracy on the rivers, a plethora of restive secret societies, salt and opium smuggling, and above all a population deeply divided between Zhuang minority tribes, established Han residents (Punti), and "Guest People" (Hakka)...

The core of devotees did not join purely because Hong professed to be the son of the Abrahamic God. Rather, Taiping religion was compatible with existing beliefs. Esherick specifically highlights the use of spirit possession by Yang Xiuqing and Xiao Chaogui as being a specifically local folk religious element, but more recently Thomas Reilly has also noted that several core elements of Taiping theology, especially the nature and place of God, explicitly appealed to a vision of classical, pre-Confucian Chinese monotheism. While this idea that pre-Confucian China was monotheistic was ultimately a Taiping contrivance, it does show that Taiping belief was not supposed to be a complete departure from existing traditional Chinese beliefs. As both Esherick and Reilly argue, Taiping religion was clearly constructed to be compatible with Chinese tradition.

The Taiping did not grow purely because of ideas, but also action, and the ethnic conflict provided an arena for that action. The Taiping started out specifically providing protection to Hakka villages, but over time seem to have shifted towards a pan-Han movement that countered and/or recruited bandits and pirates more generally. This created a pragmatic reason for people to support the Taiping, as their military success made it useful to seek their protection through membership. After the Taiping departed their Guangxi context, disgruntled elements in Hunan, Hubei, Anhui and Jiangsu, finding a means to address their grievances in the form of a roving rebel army, joined its ranks and swelled its numbers. In general, pragmatic reasons brought people to the Taiping, but the Taiping's religion and ideology seems to have been what kept people involved.

As for the relative lack of widespread knowledge about the Taiping, I'd highlight, for comparison, the American Civil War. The two conflicts were contemporaneous, and both saw the rebelling side lose to the established power. Yet one seems to have seen a lot more romantic attachment to the losing side than the other. I'd argue this is partly a matter of people in the Anglophone world not noticing: up till the fall of the Qing and even after, there were those who looked to the Taiping for inspiration or as outright antecedents: Sun Yat-Sen and Mao Zedong stand out in this regard. But one aspect that is worth highlighting is that eventually, movements that shared aspects of the Taiping's goals succeeded in bringing about lasting change: the anti-Manchu revolution in 1911 and the Communists in 1949. The obvious aspect of this is that there have been more recent political upheavals to pay attention to in China, while the US has not (yet) had another civil war since 1865; but it is also worth adding that the ethnic and socioeconomic ideals of the Taiping were at least nominally achieved in the long run, so there hasn't been much need to cling onto their symbols and legacy, unlike the use of Confederate symbols as part of subsequent racism in the US.

Beyond that, of course, the Taiping War happened in China, and while there is a strong case for saying it was an event of global interest, that its subsequent cultural memory largely took place within China limited the extent to which it would be remembered in 'Western' contexts, compared to the American Civil War, which while also a global event, also had a cultural legacy that lived in a broader 'Western' context.