The key point is that property prices remain stagnant because a property developer creates value, turning undeveloped land into condos, etc.
Building casinos requires riding property values.
Speculators would (try to) buy low and sell high, whereas a market maker could well buy high (when speculators are trying to sell) and sell low (when speculators are buying). That sounds counter intuitive, but of course speculators aren't always right, and market makers typically aren't holding assets for enough time for prices to move much, and they make money off a small spread.
A market maker doesn't hold assets for appreciation. They make money on the transactions spread, not hold and speculate. The New York Stock Exchange is a classic market maker.
Property developers are classic speculators.