A small but important correction: This wasn't an official gift from Czechoslovakia but a gift directly from the company ČKD (Českomoravská-Kolben-Daněk). Worth noting is that Czechoslovak arms industry was already exporting their products to Persia/Iran since late 1920s, Zbrojovka Brno was probably the biggest one - it sold cca 300 000 rifles total to Persia during the interwar era.

To actually answer your question, the reasons for this were purely pragmatic and profit-driven. ČKD hoped to export their AH-IV tankettes and TNH light tanks to Persia and this was an attempt to attract attention to their products.

This attempt was ultimately successful as Persia did initially order in May 1935 30 AH-IVs and 26 TNHs (known under the designation TNH-P). This order was raised in September of that year by another 20 tankettes and 14 tanks; in 1937 the Persians even expressed an interest in acquiring between 100-300 additional pieces of both vehicles, however because of the Munich Treaty and the German occupation this did not happen.

Source: FRANCEV, Vladimír: Československé zbraně ve světě: V míru i za války, 2015