I think the Democrats mistake was allowing a vocal minority to push identity politics, pronouns, and transgender athletes way beyond what the nation was ready for. Even Barack Obama cautiously waited to come down on the side of gay marriage only when the country was ready for it.There were certainly those elements, all of which dated back to the Southern Strategy.
Once the Cold War ended, both major parties scrambled to reinvent themselves. Democrats cut our defenses, both military and intelligence, setting the stage for 9/11. Republicans focused upon bigotry and xenophobia with anti-gay and anti-abortion rhetoric. Both parties become more extreme in effort to attract attention. Those in the center were left with choosing between two extremes. This is the seesaw that produced Donald J. Trump...not just once, but twice.
I don't think the mainstream Democratic party was ever hostile to a robust military and intelligence capability. Most military actions in the last 110 years were started by Democrats. And Republicans used to complain Clinton was just using his pursuit of OBL to distract from Monica