Why did some countries industrialize before others?

The question asks why some countries industrialized before others. To start, industrialization is generally assumed to mean the introduction of mass production techniques and high degrees of mechanization. As such, it has historically meant a move away from an agriculture based economy supported by artisans conducting skilled trades. Industrialization comes from two inter-related, synergistic elements, namely, the mechanization of production of existing goods, and the introduction of new goods possible only through the advance of technology and capital.

Industrialization occurs when (a) technology allows the mechanization of production and (b) the political economy of the nation allows the freedom to implement that technology. Technology development in turn requires high levels of educational advancement, and the presence of enough excess economic value over and above that required for bare subsistence. That is, there must be enough resources to support people who can do research and development. Finally, as new production processes require labor, and often require that this labor be literate and trainable in different ways of working, industrialization requires a certain degree of population mobility. The pattern of industrialization can be largely traced to the relative presence or lack of these factors.

Of course, a topic this broad and impactful will have a variety of analyses.  A good example of this deep of "root causes" analysis is the reference cited below.