AMLO wants to "develop" the Yucatan with a tourism train, forcing it to be built by the military instead of the company that won the contract.

This train runs through archeological sites, which angers the population of the Yucatan which a large chunk is Mayan.

Archeologists are rushing to excavate sites before the government comes and tears them down.

What is not covered:

The Yucatan and Chiapas have a long history of attacking the Mexican government for intruding on its territory and heritage, and peace has only happened when the government does not touch the Yucatan at all.

With racism against indigenous in Mexico increasing with "whitexicans" showing up to disrespect Mayan sites, this can very easily start another caste war or Chiapas rebellion.

This is probably why AMLO brought in the military to build it, he is trying to start an incident with the Mayans in Mexico.

You can only guess the reason why.