Firstly, you are indeed right that Cardamom is not a native crop to Guatemala in any variety. The variety grown in Guatemala, is Malabar or Keralan Cardamom and was introduced by the German immigrant Oscar Majus Kloeffer sometime in the 1914-1918 period, something for which he later received the Order of the Quetzal, Guatemala’s Highest Honor. (Georg Schulz, Zimtzicken Canehlpuper und andere Merkwür Zigkeiten) While I’ve been unable to find a source that states this outright, it is extremely likely that he started cultivating Cardamom to use it as a cash crop. The first reason for this is that he was the son of an apothecary in Hamburg, and therefore familiar with the medicinal demand for the plant in Guatemala’s main export destination. Secondly, given that he became a Finquero (Coffee Planter) in Guatemala, where planters typically grew a secondary cash crop as insurance against coffee crop failure, he may have chosen Cardamom as his backup to differentiate his output from those of other Finqueros. (Who would probably have grown Quinine or Rubber.)

It later became a cash crop because Guatemala’s North Transversal Strip (NTS), consisting broadly of Alta Verapaz, Quiche and Petén departments, have exactly the right climatic conditions for the raising of the crop. It is also capable of being grown by small farmers in forestry conditions and not particularly labor intensive, to the point where in India the growing is mainly delegated to women. (Whereas in Guatemala it is done by whole families.) Thus, even if the production efficiency is poor, at around 33 vs. the recommended 60 Quintals (1 Quintal is 101.48lb) of good per hectare (Harnessing Agricultural Trade for Sustainable Development: Guatemala) and handled by small scale enterprises, Guatemala’s climate and the large labor pool give it a significant advantage over traditional growing regions.

This then combined with an effort by successive governments to develop and “colonize” the underpopulated regions of the country. Traditionally, this was the case in the NTS due to its poorer agricultural potential in terms of growing both bananas and coffee. Thus, the growth of Cardamom production and a combination of further land reform and colonization efforts in the period after the Second World War provided a shot in the arm to the agricultural industry there. This was further galvanized by high prices for the crop in the 1970s and 1980s, leading to a further growth of production and Guatemala overtaking India as the world producer by 1979-1980.

Sources:

Brent K. S. Woodfill, War in the Land of True Peace: The Fight for Maya Sacred Places, University of Oklahoma Press, 2019.

Dennis, Philip A., et al. “Development under Fire: The Playa Grande Colonization Project in Guatemala.” Human Organization, vol. 47, no. 1, 1988, pp. 69–76. JSTOR, www.jstor.org/stable/44125982. Accessed 14 Mar. 2020.

Georg Schulz, Zimtzicken Canehlpuper und andere Merkwür Zigkeiten., Books on Demand GmbH, 2003.

Harnessing Agricultural Trade for Sustainable Development: Guatemala, UNCTAD, 2019.

Higbee, E. C. “The Agricultural Regions of Guatemala.” Geographical Review, vol. 37, no. 2, 1947, pp. 177–201. JSTOR, www.jstor.org/stable/210767. Accessed 14 Mar. 2020.

K.P. Prabhakaran Nair, Agronomy and Economy of Black Pepper and Cardamom: The “King and “Queen of Spices, Elsevier, 2011.

Reyes, Teija, et al. “Small Cardamom: Precious for People, Harmful for Mountain Forests: Possibilities for Sustainable Cultivation in the East Usambaras, Tanzania.” Mountain Research and Development, vol. 26, no. 2, 2006, pp. 131–137. JSTOR, www.jstor.org/stable/3674633. Accessed 14 Mar. 2020.