First of all, I more than most appreciate the hard work involved with going backwards and listing draft selections.
I agree in essense with all of what you have stated.
So many factors attract NHL teams and their scouts that have them gravitate towards 17 -18 year old defenders and projecting them as the future answers.
But this "ain't the NHL your father watched" (that would be me, lol) in terms of speed reaction and pace.
Skating, quick sticks, strong on the puck when in possession, and pushing the pace are now much bigger components than being the big point shot and crease clearer.
All three major junior leagues have so many teams and though the best rise to the top, that still is a top that is so below the pro game because these best junior defenders you are viewing are make it look easy against other less skilled juniors.
But before I delve into the why some of these guys get selected where they do, I just want to go backwards with the fact there are also prospects that do not get selected at all.
They come is all shapes and rerasons, but let's just spent a couple seconds on a couple of guys who weren't drafted.
Let's starts with Brenden Dillion of the Dallas Stars.
I know many a website has him type cast as third pairing water mark, but there is a two sided game. He is really good and smart on the attack, point and has the size and nasty on defense, and the fact that he leapfrogged over high pick Jamie Oleksiak, 2nd rounders Patrik Nemeth & Ludvig Bystrom just makes it more exciting.
Dillon was a midget as his draft year approached, and then as draft eligibilty was expiring, he grew like 9 inches in from 5 foot two in a year, Seattle took a chance on him and it took all his seasons there to get his feet to catch up his body and adjust to the WHL.
Teams thought about picking him in the final third year of eligibility, but didn't…and he keep growing and getting thicker and improving his skating foot speed and agility.
I actually think he is their best all around defender, because he is solid in all phases PP, and PK.
So you can believe the experts or stick with my eyes…this kid is plenty good and a big part of their future.
You can always also find "lesser lights" who teams deemed as far to undersized whose natural abilities were always instinctive, but they did not have that height and girth, like Minny's Jared Spurgeon who can be lsited at 5' 9"-168, if you want to believe press guides.
But let's get back to your main point, "Why do teams take defenders when the do?"
Let first approach it from the "Cam Barker syndrome":
Even in elite international tournaments and Junior playoff and Memorial Cup battles, young defenders with high end offensive PP skills start to stand out and scouts project them as pros especially if they have size and reach. There is a confidence that they will fill in the parts that are missing in the weight room and on the ice.
But in fact the jump from being a junior defender to a pro defender is huge in terms of the skills of the opposition, but also at the recognition and pace they now must adapt to.
I wouldn't be uncomforatble saying that teams who have attempted "quick ascensions" to the NHL with young defenders have, in general, been confidence-breaking debacles that gain the teams and youngsters little in the way of long term improvement.
Even though I could easily compile a list via your list, there are more than enough Keaton Ellerby's to go around.
There is clearly an alure to the bigger junior defenders, mostly because if they fail to be possible top pairing defensemen, teams will also think they can be possible servicable lower end ones.
Team look past the fact they lose stick battles, lack NHL quick feet, or really haven't use their size to their advantage as the progress against the higher level elite.
And let's face it, human nature has NHL organizations look for that home run if they feel their organizational depth is lacking on defense.
They will many times by-pass the smaller steady positionally reliable dee-man, if they see this junior flashy big man.
They may also "stay-home" an draft from North America, because they are more comfortable with the possible draftees they have seen many times, and know through conversations…because their character should push through easier than a guy where there is a translation of their on ice thinking and the language makes for a little harder to read their IQs on their reactions in specific game situations.
I had Bob Pulford tell me that selection the French speaker, Ray Bourque, for the Blackhawks in 1979 might be too much of an cultural adjustement for the youngster when he selected Keith Brown instead. (Ironically the organization overturned this die when forward Denis Savard was available at pick three in 1980!)
So there are so many forces at play when a team gets to the podium on any round of the draft...and maybe the biggest one is the very fact that so many draft years are NOT filled with candidates that CAN fill NHL defense corps they way the need them to.
Each draft is unique into what it's crop brings and they are never going to yield the same amount of equal possibles.
On my part of
www.Draftsite.com, I have a Re-Draft section staring with the 2000 draft up to 2009 (a little difficult to start assigning grades past this one, because there are many that are yet to display their impact as NHL regulars.)
Some of the Redraft years have enough notable prospects to warrant two rounds of redraft while others do not even show an enitre first round of thirty who warrant mentioning.
It is fun to look at which teams were able to cobble out the kids whose attributes do eventually help their team, in both big and little ways…. Bill Placzek