This is good news.
I assume the military skews young, like, 25 and younger. I wonder how much that would explain it?
The military isn't a democracy though.
If lots of soldiers decide not to vote for Trump, or to vote for Biden, that's going to have a small effect on the results. It
might be significant in swing states, but probably won't be amongst the most significant things in those states on election night.
The real importance of 'military support' for Trump is in deciding the actions (or inactions) they take when ordered to support him as CIC against what he will spin as an attempted coup d'état, if Biden's team attempt to have their man inaugurated (or even recognised as victor), while Trump's chaos merchants are still busy obscuring the result.
And that comes down to Trump's support (or otherwise) amongst the higher ranks (and therefore older demographic). There's a reason why third-world shitholes are often run by General Whoever, or Colonel Whatshisname, and rarely by Sergeant Whoisit or Corporal Thingumy.
A successful coup requires that at least some military units (or more accurately, their commanders) actively support the coup, while those who do not actively support, at least stay in their barracks.
If one side has support amongst senior officers who are prepared take an active part, and the bulk of those senior officers who lean towards the other side are persuaded that active combat on the streets of their own country is a cure that's worse than the disease, then the coup will succeed.
If the senior officers are fairly equally divided in both opinions and commitment to action, you get a civil war instead.
As both sides would likely frame a significant confusion that obscures the democratic process as a coup attempt against their side, the issue becomes not one of popularity (even amongst senior officers), but more one of readiness to lead their troops onto the streets. And that suggests that any coup might be resolved in favour of the more authoritarian and violent side.