It was pretty much a given that over time some of these airplanes would be shot down. There's no way to get every single MANPAD or even some of the larger anti-aircraft setups. A jet can even be brought down by a canon or a bullet given enough luck. We've had quite a few near misses, there's a video of an Israeli F-16 evading a surface to air missile, there have been the F-35 that was hit but managed to continue and land, there were countless drones shot down.

This was inevitable and just a question of time. Out of >10k sorties something is going to get hit. I've no idea what range the military planners expected and how we're doing vs. that.

OP left a little to interpretation, but, I think, top of the list starts with 'mission accomplished 2.0' meme followed by increased US casualties ( though I suppose the exact order likely depends on your current disposition ).