Why is this move Brilliant!!

I don't know why 25. Bd5 is a brilliant move. To me, it looks like a blunder of a rook. Any insight would be appreciated.

It has to do with how a Brilliant move is defined.  From Chess.com's own words:

"Brilliant Moves must now sacrifice material in some way and must be the best, or nearly the best, move in a position."

For the move 25.Bd5, what the computer is seeing is that you are losing material (a rook for a bishop), but that sacrificing the exchange is the best move. See how in your position that after the captures on f1, Black's Queen and Rook stand no chance against your Queen and three pieces.

If you are interested in other examples about Brilliant moves, I covered an interesting case where two mate-in-7 moves were available... but only one of them was considered Brilliant by the computer: https://www.chess.com/blog/Alramech/the-new-brilliant-move-algorithm-in-action

I looked at this for a while and concluded that there's no easy way to see why this is the best move and the only way to see why it works is to investigate lots of different lines and that's why it's brilliant. The best line for Black though is to offer the exchange of Rook for Bishop so White recovers the material quickly. The question of why that is the best line is more complicated, because Black has many options, though none of them help the situation.

The engine is tricky,  it can reward simple moves in a big way at times.  Further analysis reveals the engine considers, 25.  b4 is the best move.  In this case, 25. b4 Qc4 26.  Bc6 is now called Brilliant.  Both Bd5 & Bc6 simply prevent, RxBa8 and  protects Na7.   In addition,  1st.  Bd5 prevents 26.... Qxf1+ 27. Qxf1 Bxf1,  exchanging Queens.   Bxf1 is not a blunder because, the engine wants to keep both Queens on the board until move 31, as you played.  2nd.   Bd5 prevents Black pushing f7, connecting its Kingside pawn majority, had you opted not to take.  None of these 2 factors weigh into the brilliant rating.  Letting all three lines run, Stockfish 11, depth 20, doesn't checkmate until the 66th or the 68th move since it's not human, and have to go to work the next day!  

I wouldn't say it's a brilliant move - it's just chess.com's silly way of defining sacrifices - but I can see a very simple reason why it's better than 25.Re1. Saving a bishop for an exchange, you only lose 2 points of material; but if you move your rook, you lose a clean 3 points of material. Of course, there's also the fact that after 25.Re1 Rxa8 and your knight is in a very vulnerable situation.

guys test this on explorer or analasys: e4 e5 Bc4 Nc6 Qf3 Nf6 d4 Bb4+ Bd2 Bxd2+ Kxd2 O-O Nh3 exd4 e5 Nxe5 Qd3 cxd3 Qe7 Re1 Ne4+ Rxe4 Qb4+ Ncc3 Qxb2+ Kd1 Qxa1+ Kd2 Qxc3+ Ke2 h6 Nf4 d6 Nd5 Bg4+ Rxg4 Rfe8+ Kf3 c6 Nxc3 dxc3 Bb3 d5 a4 c5 a5 c4 Bc2 b6 axb6 axb6 dxc4 dxc4 g3 b5 h3 b4 Rxc4 b3 Bc2 f5 bxf5 c2+ Kf4 Ra4 Re4 c1=Q+ Kg4 Raxc4 f4 Qd1+ Kf5 Qd5+ Kg4 h5+ Kf3 Qd3+ Kg2 Re2+ Kf1 Qd1# I wonder how i got a brilliant on Ra4, I was trying to divide the attention from the other rook so i can get a queen. I am rated 400 blitz, this was a blitz game, I hade alot of inaccuracys and some mistakes but its ok, I'm just happy that i made a brilliant move