Doing an and over on pavement is serious. I am really glad your ok. Can you buy me a lottery ticket?

I'm not sure how the aero bars play in to the bike going over during braking, the brake levers appear to be in the 'conventional' position on the trekking bars.

The stem doesn't look excessively long, but that bike looks tall in the vertical, and short front-to-back.
If the OP isn't getting behind the saddle during hard braking, it could cause the endo.

After reading the many stories of end overs, I'd say I won the lottery with no broken bones, I'm not out of the woods yet with extreme soreness in the shoulder and in the upper left chest area, but irregardless, lucky indeed, there are some sad outcomes from cyclists going over handlebars.

Bike geometry specs are st-52, tt-54.2, headtube angle 72, headtube length 175, st angle 73.5, trailing arm 43, length axle to axle 100.4, fork rake 45

Definitely surprised me how quick and easy the ride went acrobatic.

Got back up on the bike Yesterday, did my shorter course, surprisingly shoulder and ribs felt better on the bike than when sitting or lying down. Am much more aware of my position on the bike when I touch a brake lever, I am able to shift way back on the bike for braking, just need to make it second nature. I also did something else that some may deem as controversial but in my case its good. I switched the braking for the front wheel from the left to the right bar grip. My right hand has much better fine control, and I find that I tend to hang on to the handlebars with my right hand if I am extended out on the bars and reaching back with only one hand for a brake lever. Now that will be the rear brake and the front one will take more conscious effort to pull. Awareness of which brake lever was back or front had not become second nature to me as I just began riding 5 months ago.

Sincerely appreciate all the shared wisdom, quite an ordeal going over the bars, "back in the saddle again"...

Just noticed the Scott AT-3's; That's a serious blast from the past. I used to ride with an AT-4 back in the '90's.
I remember that the grip area was little on the narrow side, and put you hands a lot closer together than a typical straight bar.

Couple the narrow bar with a grabby front brake and you might have experienced a high-side, where the front wheel skids under braking, then grabs traction, but if the wheels aren't straight, the rear of the bike tries to pass the front due to momentum. This happens very fast.
On a moto, the rider gets thrown over the bike and down the road, on a velo, the bike will come with you.

Your front wheel might have 'tucked under' and flicked you off.

I rode East Coast woods MTB for years, and been over the bars my share of times. Glad you weren't hurt.

Ugly furniture?

I had read about AT-3's on Sheldon's site, then ran into a $5 pair in a junk box at a bargain junk bike store. Slapped them on my MTB road conversion and became hooked. Months later searched for and found a large 58 cm width AT-3 still in the wrapper for this bike as I was aware of the more narrower hand positions on the bar, really though no different than drop bar upper hand positions.
Mine was an odd fall. I remember watching the front wheel as I pivoted over, I lost conscious memory at about the time I crossed over the axle vertical line. But my wounds and bruising are all on my left side, no hip road rash, so must of landed in a rotational drop on 4 points, front of edge of helmet, cheek, upper side of shoulder, top of elbow and just above the knee. I didn't let go of the handlebars until impact.
As i rode yesterday, playing with the brakes, its still a little odd that it happened the way it did as my rear wheel doesn't lift at all even with harder braking as long as I am sitting on the seat. Irregardless a weight shift, brake lever swap, and possible toe in on the front pads if necessary should help reduce future end overs.

I do so enjoy the hand positions on those bars, a grip for torquing up hills, a flat hand position straddling the corner wraps for resting from gripping, the stretched out grip on the front extensions for boosting it in the flats and the brake lever position that apparently "was" my nemesis. They are great for hands that are starting to stiffen with age.

You need to increase use of the rear brake and decrease use of the front for more of a 60f/40r split regarding lever force. Applying all the force to the front is going to give you the somersault treatment easy. You may also consider giving slightly more cable slack and opening your caliper a bit more to increase braking modulation (control) at the slight expense of braking power. Having the calipers very close to the rim makes locking up the front wheel easy. Increasing that distance makes applying braking force more of a linear transition as you ramp up the lever force.

am i the only one who thinking learning to seriously brake is good thing, instead of looking for a mechanical solution? the solution to flipping your bike is to practice not flipping it, find your limit.

I flipped my Montgomery Ward 10-speed when I was 17. I was on a long descent and decided I should scrub of some speed. Next thing I knew, I was on the ground and my bike was flying over my head. I escaped without a scratch, but pretty shaken up.

Since then, I always shift my weight rearward before I touch the brakes on descents.

I also have avoided front-mounted luggage on my bikes, but 30 years later, I'm considering giving front panniers a try.