For the Mexican case specifically, the revolution did not replace the landowning political elite, but installed a different subset of them. A succession of presidents from the landowning class slow-walked land reform (we're talking single-digit percentages of land redistributed per decade), mostly motivated by the fear of Zapatista rebels rather than commitment to equality.

Cárdenas was probably the first seriously pro-reform president (mid- and late-30s), but the old landowners remained wealthy and preserved a good chunk of their holdings. (For political reasons, he focused on foreign landholders.) This meant that the next landowner-friendly president a few years later created a land-leasing system that de facto returned control of large collective farms to the landowning class.

See also how the (non-revolutionary) emancipation of serfs in the Russian Empire didn't change much, since serfs had to take out loans to compensate their former masters. Social hierarchies and power balances remained, despite a change in form.