Why is 的 at the end of phrases such as 那是他们的 and 钱他们的? I'm confused with the possessive particle 的, it was explained to me as 's in English and &quot;of&quot; something. Like, Y的X becomes X of Y.
那是他们的。
他们的是那。

Here are two sentences that from that logic would both mean the same thing and both be correct. However, we would put 的 at the end in this case. But I'm not sure why. Another example would be:
他们的钱。
钱他们的。

Here the first sentence is correct and how I would write it, whereas in the first example I would have used the second sentence which would be wrong?
他们的钱 isn't a sentence but a nominal phrase, meaning their money.
钱他们的 could be taken as the shorthand of 这钱是他们的.
那是他们的 is correct.  However 他们的是那 isn't.  You need a measure word there.  E. g.  他们的是那个。It's hard to explain why.