Why does the engine in puzzles sometimes answer by second best move?

I often play some of the lichess tactical puzzles "Find the best move...". I sometimes wonder: Why the heck did the engine answer the best move by e.g. giving its queen or rook... And when I switch to the analyze board, it sometimes turns out, that the engine indeed could have played a better move. Any idea, how this comes?

According to me
That's what the opposition would have done in the game . The idea is for you to solve a move that would have been made by a human not machine.

also, most of the time the top move has an incredibly long line which leads to an advantage many moves later, and the puzzle can’t be that long and accurate that whole time