מצה embodies two ideas: poor man’s bread (slavery) and free man’s bread (the bread that was made in haste when they left Egypt). These ideas seem to contradict one another; how can they both exist in one חפצא של מצוה, object of the commandment?
Furthermore, if you look at RabbiRabban Gamliel’s statement that one has to speak of three things to be יצא (fulfill onesone's obligation), he only lists the one explanation of “free man’s bread”. Why is the other idea of Lechem Oni (poor man's bread) not included?