One thing you have to understand, is that these are HIGH run records. Not average runs of players. Quite often, ones high run will be considerably higher than their average runs.
I posted a 12. That is a true run. For me, a once in a lifetime run, but I did do it ONCE. My next highest run was a 10 pack, and a few 9 packs. Now, lets break it down just a little to see how that happens....
First thing you need is the ability and focus to run out when the table is runnable. That is a "given". Then, you need a "friendly" rack and the same person racking them the same everytime. Now, that does not mean pattern racking, but having the one in the same spot on the table each time. Along with the friendly rack, goes a friendly table.
By "friendly", I mean a table and racker that gives a consistent rack that just so happens to have the correct gaps in the correct places. My 12 pack was on one table, and my 9's and 10 were on a different table, but the same table for the 9's and 10. And, those were over a two week period. Played on that table many times before, and many times after, and never had the rack break open like it did for those two weeks. And during those two weeks, while playing a crew of construction workers, the same guy was racking for each of those larger runs.
What I know now, and didn't know then, was that the racker had to be consistently putting gaps in the right places by accident that made it conducive to good spreads and balls dropping on the break.
Also, besides the rack and table, the breaker has to recognize what is working, and be able to repeat it rack after rack.
Now, outside of my highest run, and those magical two weeks, my next highest run is down to a 6 pack. Did that ONCE. After that, a number of 4's and 5's. So, for those high runs people have, it's really just a moment in time when everything came together just right to give a good memory. Nothing more than that really. It's surely not indicative of ones normal play.