If I am not mistaken, LATAM Pass does not have a separate Argentine entity so tickets purchased with miles for travel on Delta should not be affected since tickets would be issued by LA and not 4M (LATAM Argentina) and visa versa. All miles are safe, just less options to use them within Argentina and travel to the US may cost more miles since no longer as many direct options (only DL)
For customers with existing LATAM Argentina operated international flights, can imagine they will just be booked on other LATAM flights and probably need to make a stop in GRU/ GIG/ ASU / LIM/ SCL instead of flying direct to wherever they are going.
Only reason I could think of would be to protect jobs within Argentina. Not sure that is gong to happen, but that would be the motivation behind a rescue such as that.
For years, Aerolineas' Camporistas directives tried to squeeze LATAM out.
Now that it is leaving, they complain about the 1700 jobs that will be lost. Amazing morons....!