It could be that the toddler was the trained terrorist and planted and set off the bomb, and then became the first victim departing through the freshly-made hole.....
However, BBC is reporting this morning that the bomb was apparently planted in the hold by someone with access to baggage loading. So why now are passengers being banned from taking hold baggage on the plane if the bomb was planted by someone airside who has access to planes? Irrespective of whether or not there is any cargo/luggage to load, if the "airport staff" have unattended access to planes, they could do what they like without question, and the whole passenger/flights inconvenience becomes irrelevant; the plane - any plane - could be targetted by ground crew. It's that side of security that needs to be tightened up further, not what is taken on board legitimately