Everything in this movie either has an explanation, or simply didn't need one.
Somehow people keep saying "well that piece of tech or car should be working like
everything else". Um, it's real simple, it only killed stuff that was operating at the time.
The camcorder that was shown obviously wasn't turned on till after the EMP burst.
The Van was dead. But Cruise, (obviously being a master mechanic by way of a
small block engine being rebuilt in his kitchen) was smart enough to tell the mech
to replace the starter solenoid which the the original one fried because someone
was trying to start the van while he EMP burst was happening, and the rest of the
electrical components in the van were OK, because they are connected to the
accessory side of your ignition switch. when you crank your car, that stuff gets turned
off momentarily. This is why you hear your radio and a/c turn off while cranking your car.
(and I know this because I have been a mechanic for the last 20 years)
As far as the Son is concerned, when they are on the hill and there are tanks and army
guys blowing stuff up, he doesn't say "let me go" like he is tied of his dad, he says
"I have to see this!!", which obviously means that in his sons mind and heart, he
needs to see the battle. It is the same as when my granddad and everyone else
went and signed up for WWII without a draft, they were compelled by their very
being to go and fight, to see the great battles that they were watching on those
newsreels and listening to one the radio. after were attacked at Pearl Harbor, it
became even more compelling to go. The son didn't want to leave his sister and father,
he HAD to. I myself can't understand this concept, but I know guys that reenlisted that
very hour after the second plane hit.
About him being still alive at the end, we don't see him die. We see a bunch of tanks and
men run forward over the hill, and the son runs out first to see the most fantastic/horrible
thing that he we ever see, that anyone, anywhere will ever see in the history of Mankind.
There is every reason to believe that some of the men ran around the legs of the tripods.
Father and daughter are in the basement, which has camera cuts and we are not sure of
exactly how long they are there, giving Robbie plenty of time to have hitched a ride on
a transport, a helicopter, we will never know his story. Just as we are there to see one
mans(Cruise) journey of survival, there are countless other stories of people here and there
making it out alive in some way, just like the son did. We see the look in the Fathers eyes and
the look in the Sons eyes before he lets him go.
I really think that kid who played the son did a fantastic job there at the last seen we see him.
I just cant get that image out of my mind of the look they give each other, its just so real.
I have a daughter, and it just makes you see a scene like that in a different way IMO.
About the tech being under the ground. Has anybody ever considered that when the
walkers were placed in the ground, it was probably done by remote control, which
is why the aliens have never been there before, just a probe to send back data.
It most likely was before humans, and perhaps even before dinosaurs. when they
arrived here, by way of some kind of electrical beam, like a transporter, they probably
didn't even know that we were here, and didn't care. and as far as there being no reason
for having the stuff under the ground, it is probably the best FTL travel plan that I have ever seen
in a movie. send your tech by REMOTE control, and then many years later, when that planet
comes up on the queue, then simply beam yourself there, no hyper-sleep crap, no having
to eat, one moment you are on your planet, then you are in your tripod walker thing
ready to terraform.
AND, AND if you really want to get into it, maybe its not like you think. Maybe the tripods
were sent to the planet at the same time as the aliens, but the only way to send something FTL that is not organic, due to their magic bean alien technology, it has to travel BACK IN TIME, which is why the stuff was already there. Then it remotely buries itself to be protected from the weather and any lifeforms that happen to be there.
So the aliens and their tripods attack all at the same time, put the tripods go first, and back in time.
Then they Beam over a moment later, and the tripods have been waiting for you all this time on earth,
and it is all seamless as far as the aliens are concerned.
plus they probably don't even consider it bad to kill us, we are just insects to them.