There is no reason an action like this can’t have a compound cause. I would guess that, in the hypothetical, the person is not actually thinking “Okay, I’ll preface this with ‘obviously’ so that I look good.” However, it is likely that, since saying “obviously” is high status, they wouldn’t think too hard about whether the thing is in fact obvious—certainly not as hard as if they were about to say something low status.
There is no reason an action like this can’t have a compound cause. I would guess that, in the hypothetical, the person is not actually thinking “Okay, I’ll preface this with ‘obviously’ so that I look good.” However, it is likely that, since saying “obviously” is high status, they wouldn’t think too hard about whether the thing is in fact obvious—certainly not as hard as if they were about to say something low status.