1.e4 c5 2. Nf3 Nf6 3. d4 Nxe4 exists only two times in the database, both won by black. It's the move recommended by engine. 3. ... d6 has 4700 games and even a name. What's wrong with 3. ... Nxe4?
I believe you are making a common database mistake. The fact is that no one really plays 3.d4 in that position and the database is factoring in the more common transposition
1.e4 c5 2. Nf3 Nf6 3. d4 Nxe4 exists only two times in the database, both won by black. It's the move recommended by engine. 3. ... d6 has 4700 games and even a name. What's wrong with 3. ... Nxe4?