Historically, many anti-drug / anti-cartel leaders are actually members of a rival cartel, and want to use law enforcement to fight their wars for them.
The Mexican government has a long history of this. The LAPD’s (well documented for over 50 years) do the same thing.
Trump is a convicted felon with lots of ties to organized crime. Nothing about him pardoning members of some criminal organizations but not others is surprising.
In related news, he signed an executive order forcing prosecutors to seek the death penalty when police are killed, and in the same day pardoned 132 of his supporters that were convicted of assaulting police officers during an event where officers were killed.