I was reading a sentence in Deutsch
Ich mag es, grossartige Kunstwerke zu bewundern.
I can translate this roughly to "I like to admire great works of art."
Now, I know that there is an infinitive clause present with the "zu bewundern", but I can't seem to find a reasonable reason for why we need the "es" after "Ich mag".
I would have constructed the sentence as
Ich mag, grossartige Kunstwerke zu bewundern.
What is the reason for es?
Without the es, you could say
Ich mag großartige Kunstwerke bewundern.
This one uses mögen as a modal verb. Perfectly okay.
Ich mag (an mir), dass ich großartige Kunstwerke bewundere.
The problem with this phrase is if you don't say who you like (leaving out es), you tell that you like yourself, and the object clause gives a reason for that self-praise. There's an implicit an mir inserted.
To avoid that, you need an accusative object. But it's not enough, you also have to refrain from the object clause above, which has ich as a subject and therefore, praises yourself. Instead, you need an infinitive clause which refers to es instead of ich:
Ich mag es, großartige Kunstwerke zu bewundern.
Now you like something other than yourself. The action of looking at great pieces of art.
Wen oder was magst du? Es.
Who or what do you like? Es.
e.g. I'm playing basketball. I'm enjoying it.
You can use es like a 'pronoun' for verbs
Correctly you would say:
Ich bewundere (gerne) großartige Kunstwerke. Ich mag es.
Then you can ask yourself what "es" is all the same as in English, where it is a frequent question (but the ones I saw didn't have a satisfying answer, so I'm not going through the trouble of searching). If I recall correctly, it has been dubbed the indefinite pronoun.
In you example however, it is definitely directed at the non-finite verb (Infinitivgruppe, and at that works pretty much like the definite article das, which rhymes so much that the best explanation I can offer is confusion of the two, because it's pretty much indistinguishable in speech "Ich mag's, großart ...".
