LearProdigy: Following from Sambo:
White would still have the advantage despite being a pawn down. 2 White bishops with 1 black knight pinned.
Perhaps, both players were taking a punt. As kevin86 mentioned, the Queen sacrifice isn't really a sacrifice. We tend to value it alot, and so whenever it doesn't get traded for the opposition's queen it feels like a sacrifice...
Anyway, if black was to defend the knight with 12...,Rc8, white would counter with 13. Be3. Leaving open, 13..., Qxc2 for black (but the queen would end up being chased away by the two rooks and giving white extra tempi to attack the king.
Perhaps, there was too much for black to calculate since most defensive moves leave white with a moderate strategic advantage.
Without considering the Queen exchange, black's approach would have seemed fairly safe.