In Japanese the particles are replaced to give more stress.

Ok, I understand now! Thank you very much again!

Glad it helped! And sorry that I forgot about the second question completely. As for your second question, it looked just a little bit off when I see it in letters but it flows okay when I say it. I'm afraid I don't have a good answer for this but I'll give it a try. I think を怒った emphasizes what the anger is aimed at instead of what caused it. In your example, トランプ大統領が言ったこと implies that the anger is aimed at President Trump. So I'd say it's fine. But if it was 机が汚いこと, then I may wonder who you got anger with about the desk being dirty? Also I guess it's usually a human or a living thing when you usually see を怒る such as 子供を怒る? I hope this helps you understand the slight difference in nuances.

Hello Takuya, First of all - I understand the difficulty to explain, as I also find it difficult to explain my own native language. I have never learned the grammar rules seriously, so I only know how it should sound. So I want to thank you for taking the time to write this answer, which is a real help for me! After reading your explanation, I think I get it! トランプ大統領が言った is a single description that qualifies the noun こと! Regarding the second question I posted, do you know if I can write - 「人たちは、トランプ大統領が言ったことを怒った。」 ? (I replaced the に for を before 怒った. It's just that in sentences with 怒る, I usually see the use of を. Thank you again very much, and good luck with your studies!

Also, since ことis by its own in the が example and こと itself means "fact" , it could be interpreted as follows depending on the context. People got angry about the fact that President Trump said (it). This may not be a perfect answer from literature perspective but this is at least what I understand as one of native Japanese speakers. Thanks!