To have entire societies based on this one alloy during that age must have meant it was mined in large quantities. However how could this be considering the lack of major copper and tin deposits in most parts of the world?
As a student of archaeology at Gothenburg university in Sweden this is one of the most well covered subjects in my education.
The reason why bronze became so widespread is, to begin with the basics, that it was high demand for it. Tools made of bronze are generally significantly more effective than their stone counterparts, you could also make specialised weapons of it, like swords, and musical instruments, jewelry and ritual objects. This would benefit both farmers, better tools makes their work easier, and warriors/chieftains as weapons and impressive ritual objects would enhance their power projection. People who did not have the necessary ingredients for bronze making, tin and copper, therefore wanted to trade for these. Those communities and leaders who had copper and/or tin were willing to sell in exchange for products they needed. The litterature listed below goes into some detail on how this situation created a quite complex trade network that spanned from Scandinavia and the british isles to Egypt and Mesopotamia.
Some of the evidence for this large trade network is chemical analyses of bronze items found in southern Scandinavia. The results show that the copper most likely originated in mines on the Iberian peninsula, Cyprus and the Alps. The tin probably originated in Cornwall.
As mentioned you can read more in the litterature listed below. Several aspects of this trade network theory are open for debate, for example exactly what goods different regions exchanged in order to buy bronze.
Fokkens, H. & Harding, A. (red) 2013, Oxford handbook of the European Bronze Age. Oxford.
Earle T., Ling, J., Uhnér, C., Stos-Gale, Z. and Melheim, L. (2015) The Political Economy and Metal trade in Bronze Age Europe. Understanding Regional Variability in Terms of Comparative advantage and Articulations. European Journal of Archaeology 18(4): 633-657
Ling, J., Earle, T. & Kristiansen, K. 2018. Maritime Mode of Production: Raiding and Trading in Seafaring Chiefdoms. Current Anthropology 59.5: 488-524
Austvoll, K.I., 2018. Seaways to complexity : a study of sociopolitical organisation along the coast of northwestern Scandinavia in the late Neolithic and early Bronze Age. Dissertation for the Degree of Philosophy Doctor. Department of Archaeology, Conservation and Ancient History, University of Oslo, Norway.
Kristiansen, K., 2018. Theorizing Trade and Civilization. In Kristiansen, K., Lindkvist, T., Myrdal, J. Trade and Civilization: Economic Networks and Cultural Ties, from Prehistory to the Early Modern Era pp. 1–24.