Let’s look at this frame-by-frame. In image #1, we have Lars just a fraction of a second before his death:

Now let’s see the first frame of that explosion:

IT’S JUST AS BIG AS HE IS. And that’s in just the first millisecond of the blast. Here’s how big the explosion turned out to be:

(Note: Image not enlarged; Same proportions as previous images)

As we can see, Lars’ first injury (aside from those “only a little broken” bones from the Palanquin crash) was a pretty sizable explosion, at least by human survivability standards.

Now let’s look at Lars, immediately post-explosion, before he hit the wall:

He is WINCING in pain there. He’s still alive, but in pain from the blast. Now here’s Lars hitting the wall:

Yup, still alive. But in even MORE pain than before. His head is fine due to the hole behind him, but his spine gets slammed right into the rock underneath that exit hole, at high speeds no less.

Now, here’s Lars just after hitting the wall:

And here he is as he begins his fall:

He’s still alive, but just barely. His expression has changed from in great pain, to quickly going limp and losing consciousness, but he doesn’t appear to be exactly dead yet.

And then he hits his head on the bottom of an exit hole on the way down:

This is the clincher. That last frame there was right after he hit it, and we see his expression go from that, to this:

Which is when he just fell over, unmoving.

In less than a few seconds, Lars suffered injuries from a human-sized explosion at point-blank range, got his spine slammed into a solid-rock wall from the force of the explosion, and hit his skull on solid-rock on his way down.

That’s how Lars died.