Casablanca-Tartakower 1924 NYC game-need to understand rationale behind one move

Yeah, looks like both players were fighting for e4. Black wants to play Ne4 and white wants to play e4.
In the game black played Ne4 anyway, but as others said Qe2 also connects white's rooks. The queen is not a big player in the opening, it wants to not get in the way and not be on a file that will open later. In 1.d4 openings often the d and c files are opening, so putting the queen on the e file is sensible.
In the game black doubled the c pawns then chose an odd way of playing. Rf6 and Na5 are completely separate ideas and Na5 was the correct one.
After something like 15...Na5 black wants to play moves like c5 Rc8 and then eventually either d5 or e5 (depending on the timing and which is permissible). With some open lines and a knight lurking where broken pawn structures roam, black should never be worse IMO.
What we got instead is, AFAIK, the most famous rook endgame ever played.
I was reviewing the moves on this game which Capablanca won playing white. On the 9th move, he played Qe2, which I cannot understand as the Queen was left completely blocked and only had the ability to backtrack. Before that move, the White Queen had a whole diagonal of white squares that could have used for movement. All books that I have read think that this move was a good one. Anybody knows why? I don't like to make moves like that as I feel I am on a dead end street but obviously I am missing something here.
Thanks in advance for the help.
1.d4 f5 2.Nf3 e6 3.c4 Nf6 4.Bg5 Be7 5.Nc3 O-O 6.e3 b6 7.Bd3 Bb7 8.O-O Qe8 9.Qe2 Ne4 10.Bxe7 Nxc3 11.bxc3 Qxe7 12.a4 Bxf3 13.Qxf3 Nc6 14.Rfb1 Rae8 15.Qh3 Rf6 16.f4 Na5 17.Qf3 d6 18.Re1 Qd7 19.e4 fxe4 20.Qxe4 g6 21.g3 Kf8 22.Kg2 Rf7 23.h4 d5 24.cxd5 exd5 25.Qxe8+ Qxe8 26.Rxe8+ Kxe8 27.h5 Rf6 28.hxg6 hxg6 29.Rh1 Kf8 30.Rh7 Rc6 31.g4 Nc4 32.g5 Ne3+ 33.Kf3 Nf5 34.Bxf5 gxf5 35.Kg3 Rxc3+ 36.Kh4 Rf3 37.g6 Rxf4+ 38.Kg5 Re4 39.Kf6 Kg8 40.Rg7+ Kh8 41.Rxc7 Re8 42.Kxf5 Re4 43.Kf6 Rf4+ 44.Ke5 Rg4 45.g7+ Kg8 46.Rxa7 Rg1 47.Kxd5 Rc1 48.Kd6 Rc2 49.d5 Rc1 50.Rc7 Ra1 51.Kc6 Rxa4 52.d6 1-0