Why Ke7 is the best move in this positon?

Having seen this position macroscopically,the black has to respond the check by white.There are many move aim to acheive it,for example,Kf8 Ke7 Bd7 Nc6 and so on.Then i am here to Compare various  moves for black.

1. Bd7 The smooth move to exchange the bishop.But the per black bishop has a vital responsibility to protect the e6- potential weak pawn.If white exchanges the bishop prematurely,the e6 pawn will probably become a long-term weakness for black.Then white can attack the e6 pawn easily,such as Qh5 - Qe2 and concentrate his rooks to pressure e6 pawn,which can put black into a worse position.

2. Nc6 The most natural move to answer the check.This move is better than Bd7,not only does it retain the c8 bishop to protect the e6 pawn,but also it can make black comfortably castle his king and set out his rook to invade from the f-file.In comparision,after black plays Bd7,the white can plays Qh5 or Qe2 to delay castling of black.

3. Ke7 The best move here.Observe this postion first,the d4 pawn is threatened now.If white plays dc,after d4,the white will lose his bishop unavoidably.Instead of dc,if white plays Nf3,the balck can cd with full of confidence because of the main transformer：dc Nd4 Qb6 Nce2 e5±. In short,the white will lose his d4 pawn without any return and the black has a clearadvantage to win material.

In coinclusion,in this position,Ke7 is the best move to respond the check by white,which can bring black a clear advantage.

Just play 10...Nc6 and that's it. You are supposed to develop pieces, not your king, right?

Who cares if the engine claims that 10...Ke7 is better when you have to play like an engine to prove it?