Why could not he be only a shepherd ? Since, already at that times, life was changing; the economy was not closed anymore and money was needed. Sheep breeding on the Apuanian Alps was not enough. And not even agriculture.
Moral of the story: quarries meant work and resources. So, all right ? And here comes something that I cannot communicate to its real end. Better if you have been there. The Apuanian Alps are scattered with small old-time quarries, exploited then abandoned. Also sited at the end of old “lizza” ways of such a size that the quarries themselves are almost dwarfed. So, a lot of work to get to the marble and little material removed. The “lizza” ways that are still there are by far more visible than the quarries they served. The reasons of this ? A lot, that I cannot fully explain; you may find good analyses in published materials; it was because of a combination of technical, economic, social and market reasons. And further, at that times quarries, grazing, and agriculture could stay together.

How is the balance between the money generated by quarries and by agricultural, pastoral and hiking activities ?  From a point of view of the mere current money flux, I am afraid that there is no story. But, as usually, the comparison of  today’s incomes with tomorrow’s earnings (or losses) is quite problematic.
Marble will be regenerated, (all materials follow a cycle), in geological ages but, for sure the present human species will not see the new marble. So we must consider marble as non-renewable; and the same the Apuanian Alps that also are not only marble.
Then, who are the beneficiaries of marble quarrying ? And here the thing is more complex, even if potentially more interesting. There are questions to which I have no answers.  Which is the impact of the Apuanian Alps on the touristic income, both referring to hiking tourism and to tourism connected to quarrying ? Which is the impact, either positive or negative, of the changes and destructions operated by the quarries ? How many people are directly employed in the quarry work, and who they are? Many quarry truck drivers do not look exactly as locals. And how many people are working in the quarry related industries ?
Who are the marble buyers ? For as little relevant it could be from and economic point of view, maybe that we are dismantling the Apuanian Alps to build palaces in the Arabic peninsula or in some other place of new (or old) rich ?
Finally, have a careful look in the territory of natural parks, not only and not specifically the one of the Apuanian Alps. Is it normal that wall drawings of the type “park corrupted” or “thieves” are so common ? Consider that for a park this should not be. And this is not only the fruit of anti-environmentalist propaganda; often these drawing come straight and sincerely from the heart of locals.
May be that administrators gave a substantial contribution in creating a negative attitude of local populations? That, beyond the screen of a park they have been occupied in  formally nice things, for their visibility, but not really coherent with their functions ? That they took profit of their positions, creating other bureaucratic structures managing a range of different things, and leaving the clean and transparent management a bit in the background ?   And that now, to stay afloat, they are too much prone to compromise ?
Of course the Apuanian Alps deserve conservation and the present way it seems to be quite a challenge, if everybody does not do his part. There are some positive clues. If you roam the Apuanian Alps, in some quarry areas, you will find signs allowing to follow the path that would have been otherwise cleared away. This is a very small thing, but this also means that an agreement was found between quarry managers and some local management or control body; otherwise, be sure, these paths would have been simply cancelled. An agreement built, however, with a boundary in mind. And here comes the point: find  boundaries, then stay within these. In this way, it is also possible to imagine what to do when the marble stock will be exhausted, and be prepared; as a matter of fact, early or later, marble will be finished, so the problem will materialise, anyway. To establish now a limit, likely different from the present one, may also allow that something will be left, once the marble is exhausted; and that, during this time, a more balanced situation between different activities can be established.

And, without the need of creating false information about Apuanian Alps landscape. A friend of mine with whom I went hiking facing one of the more visually impacting quarry areas, spontaneously told me that she was moved to cry; and she was not particularly informed nor personally particularly sensitive to environmental problems. It maybe that her sensibility suggested her of a immobile giant with no hope of escape, consumed by replete but merciless small beings.