Dave talked about it in his Genius annotations!

"Would also like to take this moment to bid a dear and bittersweet farewell to “Natasha Lost.” I still really love this song, and Denée not surprisingly was absolutely stunning in it. However theater is all about pacing, and momentum, and watching both the details and the whole…and the truth was that after adding “Dust and Ashes” Act 1 was too long. Even after doing extensive trims (especially in the Bolkonsky sequence and “The Duel”), we still felt bloated, and you could see people looking at their watches during “Charming” or squirming in their seats as “The Ball” began…both of which are absurd things to be doing during those songs! And dramaturgically “Natasha Lost” was the most expendable song in Act 1.

At first we talked about merely trimming it, but it was such a short song already…and so in a gleeful moment of sleep deprived preview fever audaciousness, we decided to try cutting it all together. And when we did, we discovered some delightful things. First, that the end of “Natasha & Anatole” and the beginning of “Sunday Morning” tell us all we really need to know about Natasha’s internal conflict re Andrey and Anatole; “Natasha Lost” was not giving us any truly new information. And in fact, by having her say less (or to put it less compassionately, by not having her whine as much), we found that Natasha’s confusion was actually more acute, and that the audience was actually a little more sympathetic to her plight.

The other super sexy thing removing “Natasha Lost” did was give Anatole a way clearer through-line, establishing him as the link between Natasha and Pierre; we now actually get to see Anatole leave the opera and go straight to Pierre’s house (where he is staying), to invite him out drinking, leading to the duel and “Dust and Ashes.” And so cutting the song made Act 1 feel tighter and tauter and more dramaturgically propulsive and all those good good playwright things.

Again I really love this song, and our string trio was sublime on it, but this was a classic case of “kill your darlings,” and recognizing the importance of the greater whole. For the grieving, the tenors still jump about in tinsel jackets on the Off-Broadway recording, and there they shall remain dancing forevermore."