Many people see the board better online...my father always stands when he plays OTB for this reason. You just see the board better.
Why are OTB games harder?

In OTB chess...it just means more. The players have to pay for a USCF membership, entry fees and often hotels and other travel expenses. When it costs money to play, players are just going to be a lot better prepared.

bear in mind that if someone has taken the trouble to go to a venue and play chess in person, they are more likely to be serious about chess. also chess.com ratings are inflated compared to OTB, about +100 for national and +200 for FIDE i would guess.

No disrespect intended, but perhaps OTBs are more difficult for you, than it is easier for the other lower rated player. Certainly OTBs are harder for me. Simply bcz of the touch move. Let's be honest, we all have tue capability to put our game settings to "confirm move". That can be huge.

Many people see the board better online...my father always stands when he plays OTB for this reason. You just see the board better.
This can be true for people that don't play OTB often. You get so used to playing online that the first few games of an OTB tournament can be a spatial mindf---. After a game or two, you can usually adjust pretty well but if those couple games go badly, it can wreck your confidence. That can lead you to a pretty bad tournament. Happened to me the first time I played OTB in 15 years.

OTB players are serious chess players who concentrate and play to win. That alone makes them much tougher than similarly rated online players
People who have played in a few OTB tournaments tend to be more determined and better at concentrating then online-only players. The are prepared to work hard the whole game, and they don't fold up when they get in trouble. These competitive traits are worth at least 100 rating points, probably more!

1. OTB uses a long time control and people blunder less in longer formats, so lower rated players won't lose as quickly or hang as many pieces.
2. As others have said people take OTB more seriously.
3. Kids have been playing chess for over a year (some adults too) with no otb games.
"3. Kids have been playing chess for over a year (some adults too) with no otb games."
I've heard that from a couple of people. I hope it's not true, because I'm getting ready to play my first OTB tournament in 18 months. The kids are getting stronger, and I'm just getting older

It's just a different scale.
Why are people that are 1200 on blitz 1800 on puzzles? It's just a different rating.
You'll see a lot more casual players online than OTB competition, so the online ratings are inflated.

"3. Kids have been playing chess for over a year (some adults too) with no otb games."
I've heard that from a couple of people. I hope it's not true, because I'm getting ready to play my first OTB tournament in 18 months. The kids are getting stronger, and I'm just getting older
Played my first tournament vs a bunch of kids (I'm a kid 😆) and most of the games took 1.5-2 hours... Went 3/4 but only one hanging piece (total!) From all of the U1400s I played. Most kids are definitely getting stronger.

"3. Kids have been playing chess for over a year (some adults too) with no otb games."
I've heard that from a couple of people. I hope it's not true, because I'm getting ready to play my first OTB tournament in 18 months. The kids are getting stronger, and I'm just getting older
Played my first tournament vs a bunch of kids (I'm a kid 😆) and most of the games took 1.5-2 hours... Went 3/4 but only one hanging piece (total!) From all of the U1400s I played. Most kids are definitely getting stronger.
It could be a pandemic effect. OTB chess has only recently returned in full force. Its certainly possible that the kids studied and played a lot online during the pandemic and now their OTB ratings have to catch up to their skill level.
The rating in chess.com is more accurate because there are more games to review. OTB play has limited data samples.

I have played thousands of long games otb. 250 tournaments.
All this premove tricks and speed skirmishes play a minor role. It's about real meat, real chess.

Just played in 3 OTB games on Sunday. Missed tactics in all 3. I think I would have found at least some online. When you don't see your opponent, I think it's easier to focus on the game. Plus the 3d aspect takes time to get used to.

It's about real meat, real chess.
And real understanding of the dc4 reti 😭😭On a serious note after like half a year I finally got around to watching that youtube video of yours. Gave me a lot to think about. I never really felt white had "good compensation" for his pawn in a lot of the a4 + b3 lines; Feel lost too often.
the smell of fear