It's a liberal polling outfit, to be sure.
"But the Military Times Polls, surveying active-duty troops in partnership with the Institute for Veterans and Military Families (IVMF) at Syracuse University
This being said, military support for President Trump is hardly monolithic. Obama turned the military into a jobs program and filled support positions with poorly-disciplines slackers and skaters who are there just for the steady paycheck and Tricare insurance. Many of them hate the president. Fortunately, many of them aren't particularly motivated to vote.
I wonder if that publication had been running articles about how Biden was going to give them better retirement benefits just before the poll....