Hi,
Just looking at the big end bearing - the outer surface looks like chrome i.e. coated in polished aluminum & the inner surface has a layer of steel from the crank pin. So it looks like the big end bush was loose & rotated. This would block off the lubrication holes & led to the seizure. OR big end to crankpin fit was too tight & led to seizure - although the engine felt free initially, so I think it's the first option. Also I believe the conrod is fitted the correct way round - with the 2 grooves facing forward.
Stuart