Why is Kh8 the best move in this position for black? Why is, according to Stockfish (depth = 28), Kh8 the best move here for black?



This is a position from a game between Emanuel Lasker and Wilhelm Steinitz, 1896.

Nb6 seems to be the natural move in this position. At least to me (an intermediate player).

Yes, there is a check at Qb3 or Bc4. But what's the big deal? The b7 pawn is protected if Nb6 is played. Bc4 is also not an option then.

It's not a machine-like move. Steinitz played this, not in this move, but in the next move. Kh8 is not even among my [an intermediate player :-( ] candidate moves.

This is the first time I am posting in stack exchange. Please excuse the bad formatting of the question. I don't know how to add PGN here so that you guys can go through the game move by move.
If you don't play ...Kh8, then for every move you consider making, you're going to have to worry about what happens if White responds Qb3+ or Bc4+. If you're analyzing variations, you always have to take into account that White might play Qb3+ on the fourth move of the sequence or something. This means that


You're going to have to spend extra time on the clock every move checking those checks.
You might mess up and miss one of those times when one of the checks works, and get a disastrous result.
Even if you don't mess up, natural moves that you might want to play might fail due to one of the checks, and you'll have to play a less nice move instead.
When White looks for tactics, he has built-in "hooks" to try to build combinations around. If there's some other weakness in your position at some point, there's a decent chance some double-attack tactics will become possible, for example.


Of course, Stockfish only really cares about the last two, but even that's enough. If you can afford the tempo, it's a really good idea to just get the king out of the way and completely quash all four problems for the whole future of the game.