Why is the が particle being used with these adjectives

Question

I'm learning the use of なる with adjectives/nouns in my textbook. I was given two examples and in both the particle が was used.

ex.1 にほんごのべんきょうがすきになりました。
I have grown fond of studying Japanese.

ex.2 にほんごのべんきょうがたのしくなりました。
studying the Japanese language is fun now (though it was like torture before).

Due to the first example having the な adjective すきな in it, I came to the conclusion that が here was used to mark the object in this sentence. Since in an earlier chapter I was taught to use が with すきな and きらいな. The general sentences of both examples also look at extremely similar leading me to believe that the が particles used in both sentences might be the same, but I don't want to throw them into the same category based on that alone and was never taught to use が with other adjectives like たのしい. Which leaves me uncertain as to why が was used in the second example. In my textbook I found an example similar to the second although this one takes the topic marker は instead.

にほんごのべんきょうはたのしいです
Japanese language study is fun

This really only confuses me even more as to why が was used in the second example. Any explanation as to why が was used in these two examples is really appreciated.

Admittedly I did ask a similar question to this one a few days ago, but not wanting to waste other people's time and thinking I figured it out on my own I foolishly deleted the question. Apologies for that, and for wasting the time of people who read my question the first time I made it.

Answer 1

Well your question is actually very fascinating because it highlights a deep difference in daily perception from Japanese to English.

は can mean "as for this" or "in regards to this thing..." it's very vague. It's like if every sentence you said was its own milky way, first you start with the sun (something marked with は) and then you get more specific to what you're actually talking about.

が however, is usually indicating a quality or attribute of the subject of the sentence.

So in Japanese you can break down a sentence roughly into:

Topic は Subject が quality です

In the case of the above, the subject (a human) is implied, and すき is a quality of that person in question.

たのしい however, means "fun or enjoyable" and is not talking about the person who likes it, but is talking about the activity itself as having some sort of inherent quality.

So すき takes が because it's a person (が) who likes/enjoys something. It has less to do with i/na endings and more to do with what the quality/adjective is attached to in the mental construction / understanding of the sentence.

I hope this helps, I tried to be clear but could not avoid the use of some jargon.