Experts are saying that the explosive was PETN, and it was placed on the Lithium battery. It explodes when it gets hot, so the remote trigger must have shorted the battery, which heated up enough to make the PETN explode.
That battery over-heating approach would be far too unsophisticated. Precise timing of the detonation is at the heart of this attack.
The method of creating the explosion to maximum effect, encouraged the user to pick up the device and look at it. The pagers emitted a sound and then after a very short interval, they exploded causing very serious injuries to the hands face and eyes of the Hezbollah fighters. The timing for maximum effect (which certainly came to pass) had to be precise, which would not be the case if the lithium battery was made to heat up. PETN explodes if heated to 200 centigrade. If as you say the battery was caused to overheat there would be too much variability in timing as this would be state of charge dependent. Great precision of timing would be required to make the attack as effective as it was. One account I have read involved a doctor saying he had never seen as many very grave injuries to eyes in his whole career. Given the rather small explosions they had to be right in front of the face to do that. The Israeli security services would have access to much more sophisticated explosive compounds than PETN. You can be sure that no expense was spared in this caper.
I think in coming days we will see that the Hungarian manufacturer is a Mossad front and that they had entire control of the supply chain and the ordering process.
As to the booby trap method, their associates would have hacked the code of the pager and hidden the explosives in a dummy component, or in an adapted battery, detonating the charge by a direct electrical connection to an unused output of the micro controller. This output would be made to go high on a special signal from the micro controller. The output line from the controller probably operated driver transistor to a mosfet switch feeding full battery voltage to a nichrome wire to ground inside the charge. The switch would need to be driven hard on so a driver would need to be placed between the controller line and the mosfet gate.
The degree of penetration of Hezbollah is extraordinary. It must be the most sophisticated black op of all time and they had to be in total control of the ordering of these pagers which were only in the hands of Hezbollah and its allies. They were not on general release.
It is probable that Mossad penetration extends to people within Hezbollah itself who ordered the pagers from the front company. How else could they have got them to be adopted and sent out to so many fighters and organisers?
They also have to have known that the supplied pagers were in widespread use already and not stored in a warehouse.