What is the grammatical topic of this shortening technique?

Extracted from an English cloze test:

.....these virtual selves exist in the same online spaces that many people use every day. And this is a new and unfamiliar phenomenon that some people might find___________ -- previously dead people were not present in this way.

1. trouble
2. troubled
3. troubling
4. be troubled
5. to trouble

The answer is 3 because the key said find troubling stands for find it to be troubling, but I don't understand why it stands for that. I want to know what grammatical topic is related to this sentence.

Solution 1:

Well, there's a lot happening here.

Here is a shorter version of the sentence in question:

This is a phenomenon that some people might find troubling.

The bold part is a relative clause. We can re-write this sentence without the relative clause, like this:

Some people might find this phenomenon troubling.

In this new sentence, the word "troubling" is an adjective, and the bold part ("this phenomenon troubling") is a small clause. The phrase "to find this phenomenon troubling" means "to feel that this phenomenon is troubling." So we can re-write this sentence again, like this:

Some people might feel that this phenomenon is troubling.