I kind of agree with you (see my edits), but it is harder to decelerate on a bike than in a car, especially going downhill - you run the risk of going over the handlebars.
I ride close to 6000 miles/year, most road cycling, racing criteriums and road races. Going over the bars because I simply grabbed the front too hard isn't even the top-20 things I worry about.
One question though, her IQ was 173? Einstein's was between 160-180.
https://news.ycombinator.com/item?id=6415373
(posted earlier in this thread) for more about the late Amazon executive's IQ score.
It's not about how big it is. It's about how you use it.
Or as TBBT mentions, Sheldon has an IQ of ~180 but he didn't know you could call soup delivery (or something like that)
Or to make a simpler analogy: Being 6ft tall helps if you play volleyball (may be even a requirement), makes no difference if you play soccer.
I braked, and went flying hard over the handlebars. I am not sure if I was going over before the manhole or not, but the hill radically changed how the brakes worked for me.
If you're not prepared for it and slam the front brake on your weight will shift forwards and you'll have lift off.
The bigger problem on a road bike are the skinny tires and twitchy handling make it very easy to fishtail and topple over when braking at speed.
I may have been leaning forward, I may have jammed the wrong brake. The bike may have had any of the problems you list. That combined with the manhole + hill speed was probably what did it.
I now use the public bike system in Montreal, bixi. Very convenient, and they're built like tanks, so I feel confident it won't happen again.
The same is true of motorcycyles, which is why you should allow greater following distance behind a motorcycle than a car, if you're in a car.
The thing is, in a car you can basically be unprepared, then mash the brakes when somethings wrong. It's possible that'll cause you to lose control, but in general an emergencey stop whether controlled or not will stop the vehicle very quickly without causing any direct injury.
By contrast, on a (motor)bike if you mash the brakes you'll slip or even tumble head over heels. You're not wearing a seatbelt; and furthermore your vehicle loses control a lot less gracefully.
If you're prepared, it's a different story since you can rearrange your center of mass, and get a good grip beforehand, but in an accident situation... a car stops much more quickly.
The only time my rear wheel has left the ground while braking is when I've tried to do it intentionally. And I've made plenty of hard stops in thousands of miles of riding.
The real limiting factor on road bikes is traction.
Disc brakes on road bikes might give a distinctive advantage, even with greater weight. Disc brake rims need not have a braking surface and thus can be lighter having less angular momentum.