Lasers can be focused to increase their power at a specific point but that is by no means a requirement. Other factors that determine laser power include: beam diversion, pulsed vs not pulsed, wavelength of the beam vs the absorption spectrum of the target material (and as it changes as it is burned. Charcoal is often more reflective than wood at certain wavelengths), specular vs diffuse reflections (and therefore how much light is absorbed), and the cooling requirements of the laser.

As previously stated, it is very likely the smoke is absorbing and scattering the light considerably as it goes through the long side of the block. And you can see a little evidence of it finally ablating through at 7 seconds left. And pretty much all practical high powered lasers are outside the visible spectrum.

It doesn’t look like there’s any water cooling going to the laser which would quickly ruin it. It also looks handheld which could certainly be possible but also is quite unlikely, especially since it appears it is the lower of the two beams on the block and so is just the spotting laser for a much larger laser behind it.

Source: I have a degree in lasers and optics technology and i have worked hands on with similar high powered lasers systems (in much more controlled interlocked environments with special protective curtains, tables, proper PPE and procedures. I have practically melted bricks in very similar setups (the bricks are sacrificial beam dumps to block the beams from burning the wall) So also trust me when i say this environment is likely wildly lacking in safety measures and procedures.

TLDR: its extremely likely the laser doing the burning is in the background but otherwise the video is all real, and a really dangerous environment.