Politics is often a lot about timing. I can understand the reluctance of the military leaders to remain silent as long as they did.
When I first saw Mr. Trump holding a Bible in front of church. I saw it as a tipping point. The generals must have felt the same--and could not longer hold back.
Prior to the photo-op, Mr. Trump had a 50% chance of winning the election in November. Now it is 10%--and I'm giving 10% because the D's could screw things up.
Had the photo-op happened six months ago, Sanders, Warren, or Yang (the D's with a vision) could be carrying the D flag rather than the safe not-Trump bet of Mr. Biden. Timing!