While a maximum of 20 years prison sounds rather harsh, intentionally crashing a plane is no joke or laughing matter. It's unfortunate that things had to end this way. The FAA does not mess around.
If you have a look at Google maps, within a 3 to 4 mile radius, there are multiple kids camping grounds. Even assuming they are only sporadically occupied this is a new level of recklessness.
[I watched the video (iirc) about a week after all this originally went down. Watching an airplane just kind of cruise around on its own was pretty horrifying. But I did feel a little bit better that afterwards he had to hike around seemingly forever to find someone to give him a ride. Like, at least things were remote, and he's lucky that he didn't die trying to get back to civilization.
However, apparently he thought about this as well, because nope, there's stuff all around that area. This is shooting a gun into the air to see if the bullet will come down and hurt you, but instead of doing it in a dry lake bed you do it right next to a children's hospital so you have someplace to go in case you do get hurt.
The other side of hanlon's razor is "sufficiently advanced stupidity is indistinguishable from malice".]