Why was agustin de iturbide eventually overthrow

Agustín de Iturbide, a top Spanish official born in the metropolis , was an ephimeral emperor of Mexico and Central America.

Explanation:

Iturbide was for a long time a royalist and fought the Mexican independence fighters successfully. However, as other conservatives did, he rejected a liberal coup d´état that had taken place in Spain. Then, he allied his army with former enemy forces and at Iguala, he proclaimed the so-called Plan de Iguala on February 24, 1821, which declared independence from Spain. Iturbide crowned himself Emperor of Nueva España Agustín I a year later. He often took arbitrary decisions,  was seen as extravagant, and some economic decisions proved erroneous.  He was unable to win support, alienating many sectors. He was soon overthrown - his rule didn´t last one year - and  he marched into exile to Europe. After his return to Mexico, he was arrested and executed.

the answer is b. hope this !