I bet he lost a lot of those games while he was moving up the ranks. But some 300 to 400 level players can play really well. They just haven't played enough games to reflect their true ELO. And if you make a few wrong moves/guesses or have a setup that favors your opponent, you can lose. Never underestimate your opponent based on ELO score.
Of course, there are some top players lurking in the lower ranks and like to play there to practice different strategies. Watch this game.
Dobby , this is 2017 only .I was not moving up through those levels , I was last below 500 in March 2015.
I think true ELO is reflected in 80 games at most (except perhaps the very best players ) . If i see players with a record like '28:9' and ELO 337 , then you can be sure their true ELO is not much better than 400 . When an unknown player has played 30-40 games and is undefeated or lost only one , then it is hard to tell .Maybe they are 1000 level or perhaps just 700 (which is a huge difference ) .
I agree that mistakes + set up being a poor match for their strategy does lead to losses to lower players.
A typical loss for me vs someone on 300 or so would be like this ..
I give away a Colonel for little gain through carelessness/complacency , then opponent brings Marshal to threaten an area where i don't have spy . I pretend my marshal is spy and then he exchanges marshals. Then it turns out he has an 'exchange strategy' where the aim is just to exchange highest pieces .It's quite primitive and unimaginative ( they even continue it when they are losing ! ) but these players will have their highest pieces arranged to go to the front in order of rank .So , if they are up a colonel and marshals are exchanged then they will have their colonels in your territory before you can get your last one out , and of course you may have to move more pieces just to do that , and , early in game , they will still have scouts to find some trapped pieces etc
Strangeplayer , the guy in that video , is more like 900 ELO , but he did say he was strange i guess...