A diagram that best shows why 1. Rxf5, even if followed up by 1...gxf5, is stronger for white than 1. Nf6+ is included in post #98 courtesy of rise512. And 1. Rxf5 Qxf5, as in the puzzle line, is obviously strong for white.
If 1. Nf6+ then 1...Bxf6 does not turn out as well as 1. Rxf5 for white, primarily because the g-file is not open as in the 1. Rxf5 gxf5 line. The line 1. Nf6+ Bxf6 2. gxf6 does not work for white due to 2...Qxe3. White does not have 3. Qg2+ in this line because the g-file is not open. And white does not have time to play 3. Rxf5 now because black can respond 3...Qxe2.
I laugh at all of the idiots below 1500 proclaiming how easy this is
In my opinion, replying "easy" to any daily puzzle is really pathetic, no matter the responder's rating, or the puzzle's actual difficulty.
there's still one move
after gxf6+... Kh6 Qf8+ Kh5 Be2+ Qg4 Bxg4#