“To” is usually the correct preposition that goes with the adjective “obvious”.
We use “obvious to” especially when followed by the person.
It was obvious to me that he was drunk.
It was obvious to me that she needed help.
When something is “obvious to you”, it is easy for you to perceive.
It was obvious to me that the baby needed to be changed.
It was obvious to everyone concerned that he needed to go.
“Obvious for” is a common mistake in English when used in the context above. To and For often cause people difficulties in English.
We can use the preposition “for” when it is needed to connect “obvious” to another part of the sentence.
That has been obvious for years.
(we use “for” above to show a duration of time)
“Obvious from” is more common than “obvious for” and is again used depending on the context.
It is obvious from the context.
It was obvious from the fan’s reaction.
We use “obvious from” when it is not a person but a thing or idea that something is perceived from.