There's a good point there but I think it's even a bit more nuanced. Castro's father did not come from old money. From what I understand he was born a poor peasant in 1875 and spent the first quarter of his life doing hard labour and military service. Fidel wasn't a pure bourgeois class traitor - he was from an upwardly mobile family that hit a limit. There's an interesting bit in a book about this:

Speaking broadly, it seems to me activist milieus can best be seen as a juncture, a kind of meeting place, between downwardly mobile elements of the pro­fessional classes and upwardly mobile children of the working class. The first consist of children of white-collar backgrounds who reject their parents' way of life: the daughter of a tax accountant who chooses to work as a carpenter, the daughter of veterinarian who chose to live as a graphic artist, the son of a middle manager who chooses to become a civil engineer or professional activist. The other consisted of children from blue-collar backgrounds who go to college. In historical terms, both correspond to a classic stereotype. The first repre­sents the classic recruitment base for artistic bohemia; if not children of the bour­geoisie, as they were often assumed to be in 1850s Paris, where the term was first coined, then children born to members of administrative or professional elites, living in voluntary poverty, experimenting with more pleasurable, artistic, less alienated forms of life. The second represents the classic stereotype of the revolutionary, particularly in Global South: children of the laboring classes (workers, peasants, small shop-owners even) whose parents strived all their life to get their sons or daughters into college, or even who managed to get themselves bourgeois levels of education by their own efforts, only to discover that bourgeois levels of education do not actually allow entry into the bourgeoisie, or often, any sort of regular work at all. One can compile endless examples among the ranks of the last century's revolutionary heroes: from Mao (child of peasants turned librarian), to Fidel Castro (unemployed lawyer from Cuba), and so on. In fact, both bohemia and revolutionary circles have historically tended to be a meeting place of both.

Obviously this is a highly schematized picture. First of all, it leaves out some significant groups entirely: for example, those who adopted bohemian lifestyles because their parents were bohemian, or the children of professional activists. One should not underestimate the degree of self-reproduction in such sub-class­es. Also: while the stereotype of the bohemian as rich kid-secretly supporting his absinthe habits with money from home, eventually either to die of dissipa­tion or go back to the board of daddy's company-is strikingly similar to the stereotype of the activist as trust-fund baby, it is probably no more accurate. Certainly there have always been scions of the bourgeoisie in both milieus, all the more influential for their money, social skills, and connections. But bohemian milieus of the last 150 years never really consisted primarily of children of the up­per, or even professional, classes. As Pierre Bourdieu (1993) has recently shown, the social base for nineteenth century bohemian culture in Europe emerged, in part, through exactly the same processes that shaped social revolutionaries in the Global South: among talented children of peasants, for example, who had taken advantage of France's new educational system, and then found themselves excluded from conventional elite culture anyway. What's more, these milieus tended to overlap. Bohemia was full not only of working-class intellectuals and self-taught eccentrics, but outright revolutionaries. The friendship between Oscar Wilde and Peter Kropotkin was not atypical; actually, it could be taken as em­blematic. Similarly, revolutionary circles have always been filled with children of privilege who have rejected their natal values: Karl Marx (lawyer's son turned penniless journalist) being the archetypical example. Every Mao had his Chou En-Iai, even Castro had his CM. The constitution of both milieus, then, is really quite similar. Which probably helps explain why artists have felt so consistently drawn to revolutionary politics.