Beyond dangerous
Interesting to see the core with shear walls remain intact on the way down.
That core was the elevator core with massive poured rebarred sections of hydraulic contrete. The outer sections were blown first, then the interior cores were blown in sequence with much more powerful charges— again in sequence. It left quite a pile tough concrete and rebar in the center pile as you observed.
All the rebar was separated from the concrete mechanically (cannot imagine this) and the rebar was smelted in recycling facilities back to refined steel for various applications.