This is an interesting problem, which was comprehensively investigated by Eric Hobsbawm and Joan Wallach Scott in a seminal paper published in Past & Present 89 (1980) titled "Political shoemakers".

Hobsbawm and Scott provide abundant citations to show that shoemakers were indeed considered unusually radical in the late 18th and 19th centuries. Richard Cobb, the historian of the French Revolution, for instance, describes their perceived radicalism as "an undeniable social phenomenon." More than that, they actually were radical; for example, "of the persons active in the British Chartist movement whose occupations are known, shoemakers formed much the largest single group after the [much more numerous] weavers"; at the time of the Swing riots in England in the 1830s, "the average riotous parish had from two to four times as many shoemakers as the average tranquil one"; and shoemakers formed the majority of the Cato Street Conspirators, who in the 1820s plotted the violent overthrow of the British government. Hobsbawm and Scott add that this reputation was international (for example, "shoemakers and carpenters were the first members of the Federation of Workers of the Argentine Region (1890)", and that as late as the time of the Paris Commune they were noted for their "traditional militancy". All in all, the shoemaker was "known for his love of liberty and his role as the village politician. As a social group, they were admired for the 'independence of their opinions'."

The authors explain this radicalism as the product of a combination of linked factors, and suggest it had quite a history – "in Act 1 of Shakespeare's Julius Caesar, a cobbler appears leading a crowd of protesters through the streets."

First, shoemakers were "exceptional" as "worker-intellectuals and ideologists". Shoemakers were more than averagely literate, at least in part because their work was less physically arduous than, say, farm working, and left them more time and energy for study – "probably it was physically the least taxing labour for men in the countryside." The authors suggests, as a corollary, that it was a trade often taken up by the "small, weak or physically handicapped" – men who would have had every opportunity to develop a sympathy for the downtrodden, the bullied, and the marginalised. Later in the paper, Hobsbawm and Scott also draw attention to the fact that shoemakers worked with leather, which they often prepared and tanned for themselves, placing themselves in the company of a particularly low-status group of men associated with "uncleanliness" – tanning generally involved the use of both urine and excrement in the production process.

Literacy, in turn, made it more likely that they would read and pick up on published radical views, and also more likely to spread such ideas – the authors give numerous example of the shoemaker as "journalist and versifier, preacher and lecturer, writer and editor," adding that "it may be supposed that such persons would draw special attention to themselves in a largely non-literate society." Once again, this reputation was an international one. A Russian character in a Gorki book was "like so many other shoemakers, easily fascinated by a book."

Second, shoemakers were frequently both self-employed and itinerant, meaning that they had more opportunity to encounter a variety of political views, were far more independent than most artisans, and far less likely to be beholden to a boss or squire who might take exception at any expression of radical political views. Hobsbawm and Scott posit that "it may that the relatively primitive division of labour in shoemaking allowed or compelled vast numbers of shoemakers to work entirely alone." Henry Mayhew, similarly, argued that "it was the solitude of their employment, developing their internal resources," that resulted in their being "a stern, uncompromising and reflecting race." Hobsbawm and Scott add some stats that suggest that shoemakers were more likely than members of most apprenticed professions to be journeymen (people who had not attained, or more likely could not afford, to pay all the guild dues and charitable donations associated with the rank of master), and – because this, in turn, made it harder to settle in a specific place and build a profitable business, "journeymen were notorious and prolonged travellers." A Swabian cobbler cited in the paper "worked in seventeen establishments in fifteen different places" during his apprenticeship, finding that there were "much-travelled and intelligent people among the journeymen. So I heard and learned a great deal." He eventually settled down and became a social democrat activist. The "heard and learned" is what is especially important here – the authors show that itinerant shoemakers gathered and exchanged views at inns, and, in small towns, congregated together in small workshops where they often took turns to read aloud, or paid a "reader" to entertain them as they worked – in a profession that was certainly a lot less noisy than that of, say, blacksmith. Readers, they show, typically read out the content of newspapers as well as books. And the nature of the shoemaking trade itself offered "thinking and discussion while working".

Third, the craft of shoemaking itself had traditions that helped to shape the cobblers' mentality. Hobsbawm and Scott point to an inherent pride in involvement in a trade that was "indispensable to high and low" that made shoemakers' more than usually likely to be irritated by being condescended to; yet, at the same time, there was also a division – Hobsbawn and Scott call it a "fissure," actually – between high class shoemakers, who made and repaired shoes, and low-class ones, who focused on repairs. Shoemakers proper were more likely to be urban and members of a guild. Cobblers were more likely to be rural, poorer, and itinerant, which tended to make the members of the latter group resentful.

Itinerancy had some interesting aspects, in this context. The authors comment on the lightness of a cobbler's kit (again, there is an instructive comparison to be made here with other trades, such as wheelwrights), which "actually made it easier for him to carry books with him". Yet cobblers, specifically, were also intimately associated with poverty – because costs of an apprenticeship were minimal, as were the costs of kit, "families which could not afford to bind their sons to a more prosperous, exclusive (and more costly) trade could scrape together the fees", and because there was more demand for mending services (which paid little) than shoemaking proper, earnings were often at or below subsistence level. The authors cite some statistics to back all this up – for example, in Marseilles in the 1840s, shoemakers "earned an average daily wage of only three francs... which placed them lower in earnings than many unskilled labourers." As a result, there was a proverbial (literally) link between poorer and more rural shoemakers and want. A Yiddish saying had it that "all shoemakers go barefoot", while in the Hamburg area, a dish made of leftovers was called a "shoemaker's pie".

Fourth, there is some interesting discussion in the paper regarding distribution patterns of work and workers in the early industrial era. One key finding is that shoemakers were more likely than the members of many other trades (wheelwrights and builders are instanced) to have a high proportion of clients among the poorest classes; this meant that they saw and understood the divisions of society. The authors also conclude that "the more literate artisan shoemakers... were unusual in being widely distributed in predominantly rural and small-town environments, where they could become unofficial clerks or labourers' intellectuals," and hence not only be noted for their views, but also have the opportunity to proselytise. They point out that guilds, which are typically bastions of a certain sort of privilege, did not operate outside towns and that it was impossible for urban guildsmen to monopolise the provision of shoemaking and cobbling services in villages, if only because demand was so high (everyone needs shoes, and wears them out) that no urban business could supply the entire needs to the rural surroundings.

All in all, Hobsbawm and Scott conclude,

"the village shoemakers' life was akin to that of the poor, not the rich and powerful. He had little use for hierarchy and formal organization... He knew the value of independence... It is natural to find radical shoemakers reading Cobbett, who cried out against the demolition of all small tradesmen and who denounced a system which replaced 'master and man... every one was in his place and every one was free' with 'masters and slaves'. Nor is it surprising to find them in the ranks of the sansculottes and later of anarchists. In all cases, the insistence on modest means, hard work and independence as solutions to problems of injustice were within the experience of village shoemakers."