what exactly did Porifirio Diaz do that was so wrong that led to the revolution?

Answer 1

He tried to hold onto power by subverting the electorial process

"Díaz embarked on a program of modernization, attempting to bring Mexico up to the level of a modern state. His principal advisers were of a type called científicos, akin to modern "technocrat" economists, because they espoused a program of "scientific" modernization. These included the building of railroad and telegraph lines across the country, including the first Mexican railway between Veracruz and Mexico City. Under his rule the amount of track in Mexico increased tenfold; many of these rails remain in operation today without remodelling. He introduced the idea of steam machines and technological appliances in industry and invited and welcomed foreign investment in Mexico. He also encouraged the construction of factories in Mexico City. This resulted in the rise of an urban proletariat and the influx of foreign capital (principally from the United States).
Early in his career, Díaz realized that the principal foreign threat to Mexico was the United States, and that the Mexican army stood with no chance of defeating the U.S.A. Díaz adjusted Mexican foreign policy to keep the peace with the U.S.A., reduced the size of the Mexican army and used the peace dividend to put Mexico's budget into better condition.
The growing influence of U.S. businessmen, already a sore point in a Mexico that had lost much land to the United States, was a constant problem for Díaz. His modernization program was also at odds with the owners of the large plantations (haciendas) that had spread across much of Mexico. These rich plantation owners wanted to maintain their existing feudal system (peonage), and were reluctant to transform into the capitalist economy Díaz was pushing towards because it meant competing in a global market and contending with the monetary influence of businessmen from the United States.
Though he wished to modernize the country, Díaz by no means opposed the existence of the haciendas, and in fact supported them strongly throughout his rule. He appointed sympathetic governors and allowed the plantation owners to proceed with a slow campaign of encroachment, using the Ley Lerdo, onto collectively-owned village land, and enforced such seizure through his well-equipped rural police (rurales).


Díaz - Creelman interview, Pearson's Magazine, 1908.
[Collapse of the regime

In a 1908 interview with the U.S. journalist James Creelman, Díaz stated that Mexico was ready for democracy and elections and that he would step down and allow other candidates to compete for the presidency. The governor of Nuevo León Bernardo Reyes announced his plans to run for president. However, Díaz sent Reyes on a mission to Europe, so Reyes was unable to compete in the elections.
University of California, Berkeley–educated Francisco I. Madero answered the call for candidates. Although Madero was very similar to Díaz in his ideology, he hoped for other elites in Mexico to rule alongside the President, unlike Díaz. Díaz, however, did not approve of Madero and had him jailed during the election in 1910.
Despite this, the election went ahead. Madero had gathered much popular support, but when the official results were announced by the government, Díaz was proclaimed to have been reelected almost unanimously, with Madero gathering only a minuscule number of votes. This undisputable case of massive electoral fraud aroused widespread anger. Madero called for revolt against Díaz, and the Mexican Revolution began. Díaz was forced from office and fled the country for France in 1911. Madero was assassinated in 1913.
In 1915, Díaz died in exile in Paris; he is buried there in the Cimetière du Montparnasse.

Answer 2

Like contemporary "populist" statemen, Porfirio Díaz had changed the constitution of his country to allow everlasting re-election. Madero was one of the multiple candidates who asked to limit re-elections. Porfirio Díaz jailed him.

According to Wikipedia:

In a 1908 interview with the U.S. journalist James Creelman, Díaz stated that Mexico was ready for democracy and elections and that he would step down and allow other candidates to compete for the presidency. The governor of Nuevo León Bernardo Reyes announced his plans to run for president. However, Díaz sent Reyes on a mission to Europe, so Reyes was unable to compete in the elections.

University of California, Berkeley–educated Francisco I. Madero answered the call for candidates. Although Madero was very similar to Díaz in his ideology, he hoped for other elites in Mexico to rule alongside the President, unlike Díaz. Díaz, however, did not approve of Madero and had him jailed during the election in 1910.

Despite this, the election went ahead. Madero had gathered much popular support, but when the official results were announced by the government, Díaz was proclaimed to have been reelected almost unanimously, with Madero gathering only a minuscule number of votes. This undisputable case of massive electoral fraud aroused widespread anger. Madero called for revolt against Díaz, and the Mexican Revolution began. Díaz was forced from office and fled the country for France in 1911. Madero was assassinated in 1913.

Answer 3

smells like homework i suggest you try looking for the answers yourself on google or wickepedia.