The flag is related to the 1974-1989 People's Republic of Benin, when the country was officially a Marxist-Leninist socialist one party state, under the control of the People's Revolutionary Party of Benin.

This turn was taken under Mathieu Kérékou, who had been president since seizing power in a coup in 1972. Kérékou, upon establishing the new regime, aligned the country with the USSR, attempted to implement an industrialisation policy, pursued an anti-religion campaign, and also imprisoned political opponents, all while fending off a coup attempt in 1977.

Economic policies and general mismanagement led to skyrocketing foreign debt and economic stagnation, and the anti-religion campaign alienated religious leaders from the regime. IMF debt restructuring led to wage freezes, privatization, and liberalization, which in turn set off protests that led in 1989 to an agreement to implement a new multiparty constitution the following year, with Kérékou losing a re-election bid in 1991.

Kérékou would later win a presidential election in 1996 and a controversial 2001 election, but was barred by the constitution from standing for election again in 2006 (he died in 2015). Despite this political comeback, the Marxism-Leninism was left by the wayside: in his second presidential career Kérékou was a born-again Christian.

I would take this over to /r/Vexillology. They love this kind of stuff.