I don’t have evidence of a large pool of molten steel. There’s Leslie Robertson who described a trickle of molten metal, which he called steel but didn’t get tested, running down the walls of the sub-levels. There’s a firefighter who describes “molten steel, running down the channel rails”. This firefighter looked like Frank Zappa and had a similarly colourful turn of phrase. But if he saw molten steel, what were the “channel rails” made of? Titanium or something? They must have been made of something with a higher melting temperature than whatever was running down them or the molten metal would’ve melted them too.
There are photos of glowing metal being pulled out of the debris pile; glowing, but not molten. There’s an impression of radiant heat coming out of that hole, but the workers were working by floodlight.
Energy sources? Well, there were severed gas and electricity mains, all the oil in the tens of thousands of viscous dampers the Twin Towers needed to prevent motion sickness, all the fuel of office contents including paper, cardboard, wood, fibreboard and especially plastics, all the sulphuric acid of the batteries in the uninteruptable power supply rooms for data centres in the Twin Towers, presumably the oxygen cylinders of the ~300 firefighters who perished in WTC2, all the lithium batteries of however many laptops were in the buildings at the time, all the acrylic carpets, however much ammunition that many US Americans keep in their office drawers, the aluminium of the aircraft wreckage which could undergo a thermite reaction with steel, and all the things I haven’t thought of yet.
Enough of the above for 110 storeys, all compressed into less than a tenth of the volume and nicely insulated in the sub-levels with a load of concrete rubble from the floor assemblies on top. The collapses themselves must have been like a combined compression / combustion stroke of a cylinder in an enormous combustion engine, all that fuel-air mix. Oh, and the jet fuel.
I doubt there was a shortage of energy.
It’s easy to say “lots of heat, therefore demolition” but the plausibility is superficial.