I am learning a bit of Evans Gambit theory lately, and when exploring a Master level games database, I have found this surprising line.
[FEN ""] 1. e4 e5 2. Nf3 Nc6 3. Bc4 Bc5 4. b4 Bxb4 5. c3 Bc5 6. d4 exd4 7. O-O
After it concludes, Black doesn't take the free pawn on c3 that allows them to be it to be two pawns up after White retakes. Why does White allow Black to take another pawn, and why does Black reject it?