Let me take a shot of this question, and please anyone correct me if I am wrong,

This is quite an interesting question because it can have many different facets. First, contrary to what people may think, Mexico has a deep history of welcoming immigrants, particularly of European descent, and refugees. For example, after the Mexican independence there were various migrations of Italians (particularly from the north), and French in order to populate the vast territory. Also, after the defeat of the Republic forces in the Spanish Civil war, Mexico received several waves of refugees. So the decision to welcome Russians fleeing from the Moscow Trials (the purges) was not out of the ordinary. Especially when you consider that at the time, President Lázaro Cárdenas was trying to fulfill the promises of the revolution by engaging with several sections of the population, including the Confederation of Mexican Workers (CTM), who was a prominent leftist organization.

Now, why did Trotsky choose Mexico? Because he was running out of options, particularly after the killing of Bolshevik leaders Zinoviev and Kamenev, the next one in line was Trotsky. At that time Stalin had requested that the social democrat Norwegian government handed back Trotsky, with threats of economic or political sanctions. Also, Trotsky’s Norwegian hose was occupied and the Bolshevik leader was on the brink of deportation since all of his request for political asylum had been turned down, including the one sent to president Roosevelt. After Roosevelt declined asylum, the American Committee for the Defense of Leon Trotsky (the ACDLT) met with Anita Brenner, a trotskist and member of the Socialist workers party, who lived in New York but had family in Mexico with ties to President Lazaro Cárdenas. The meeting was to see if there was a remote chance for President Cárdenas to accept an asylum request from Trotsky.

On November 21, 1936, Diego Rivera, also a militant Trotskyist received a telegram from Anita Brenner to start the request for Trotsky to be accepted in Mexico as a political refugee. Immediately, the Buró politico of the communist party in Mexico (who was mostly Stalinist but had some prominent Trotskist) arrange a delegation made by Diego Rivera and Octavio Fernandez (who was the official representative in Mexico of the Fourth International, the group of communist parties who followed Trotsky’s ideals rather than the Stalinist) to see President Cárdenas and make the request for political asylum for Trotsky, given the urgency of the case since the GPU (State political directorate, under the NKVD) were close to arresting him in Norway.

Rivera and Fernandez, inmediatly went to see General Francisco J. Múgica, then Secretary of Comunications and Public Works, who was a prominent leftist working in carrying out the reforms of the 1917 constitution and a very good friend of President Cárdenas. General Múgica wrote a letter for President Cárdenas that was going to serve as a presentation letter so that Diego Rivera and Octavio Fernandez could see Cárdenas immediately. Then, Rivera and Fernandez travelled all the way to the city of Torreon where Cárdenas was handing out land to campesinos. They gave Múgica’s letter to Cárdenas assistant, who then allowed them to see the president.

Cardenas was already aware of the petition, and before giving an answer he wanted to talk with the representative of the Fourth International. In that meeting between President Cárdenas, Diego Rivera, and Octavio Fernandez, the petition to accept Trotsky in Mexico was granted. What is interested is that he was accepted not as a prisoner but as a political refugee, given the circumstances that were threatening Trotsky’s life in Norway. The only condition that President Cárdenas requested was that the Mexican Trotskyists abstained themselves of any public demonstrations that could antagonize Mexican Stalinists.

However, Trotsy’s request for asylum was not yet a done deal. After the meeting, Rivera and Fernandez travelled back to Mexico to arrange getting a visa for Trotsky. They went to talked with Secretary of Foreign Affairs General Eduardo Hay who denied the request for a visa. Keep in mind that Eduardo Hay was also a leftist but a follower of Stalin’s ideas. Rivera and Fernandez went back to see General Múgica to persuade Cardenas to override Hay’s decision. Also, Mexican Stalinists of the CRM wanted to show President Cárdenas that allowing Trotsky to enter into Mexico could create political turmoil.

In December 5 of 1936, the Trotskyists of the communist party got together to solved the impending issue. They integrated a new delegation headed by Octavio Fernandez. With him, there were also Jaun R. de la Cruz and David Urzúa from the SUTC, (Sindicato Unico de Trabajadores de la Construccion), Manuel García from the CT (Confereracion Obrera) and Genaro Gómez Jr. from the Campesina Casa del Pueblo. This time, however, Diego Rivera stayed in Mexico city in order to keep communication with General Múgica.

Under the impending chaos, President Cardenas sent a telegram to Eduardo Hay explaining to him the reasons for granting political asylum to Trotsky. Another telegram was sent by the Secretaty of the Interior Lic. Silvestre Guerrero ordering the preparations for Trotsky’s arrival. With this knowledge, the delegation headed by Fernandez presented their gratitude to President Cárdenaz.

Finally Fernandez and Daniel Rebull, a Spaniard from the Partido Obrero de Unificacion Marxista (POUM) arranged the security measures to safely bring Trotsky from Norway to Mexico.

This narrative is mostly based in the account that Octavio Fernandez gave to the newspaper La Prensa in 1956.