I'm trying to figure out why there is "to be" instead of "is" in the sentence

Question

Why do I have to put "to be" instead of "is" or "will be" in the sentence below. Could you explain what grammar rule this is? What I should seek in Google?

I didn't expect the graphics of the video game to be detailed.

I mean graphics turned out better then I thought.

Answer 1

When we use the verb expect to refer to a future probability, and the meaning of the verb expect is "to anticipate", the pattern is

expect something|someone will + {bare infinitive}

or

expect something|someone + {marked infinitive}

or

expect something|someone to be {adjective phrase}

or

expect something|someone will be {adjective phrase}

I expect the app will crash.

I expect the app to crash.

I expect the app to be buggy.

I expect the app will be buggy.

When speaking of an anticipated future possibility in the past, the pattern with will is not used.

I expected the app to crash.

I did not expect the app to crash.

I expected the app to be buggy.

I did not expect the app to be buggy.

But you can use would instead of will:

I expected the app would be buggy.

NOTE: A relatively small subset of native speakers, not all of them, use the verb expect also to mean "believe" or "suspect" and for these speakers the following non-standard pattern is available:

expect something|someone is|was {adjective phrase}

What is wrong with the dog? It's just lying there.
-- I expect it is sick.

or past tense:

What was wrong with the dog? It was just lying there.
-- I expect it was sick.