If Moses (as) was a prophet for the Israelites, then why was Pharaoh punished for rejecting him?

Hadrat Musa ^as [Moses] was not sent to Pharaoh to only have the Israelites freed from him, he was also sent to preach to Pharaoh. Allah Almighty says:

Go thou to Pharaoh; he has rebelled. And say to him, ‘Wouldst thou like to be purified? And I will guide thee to thy Lord so that thou mayest fear Him.’

(Surah an-Nazi‘at, 79:18–20)

As a result of Hadrat Musa’s ^as preaching, he had followers among the Egyptians as well. Allah Almighty says:

And a believing man from among the people of Pharaoh, who concealed his faith, said… 

(Surah al-Mu’min, 40:29)

We also find that Hadrat ‘Isa ^as preached to the Buddhist people who were living near the Israelites. The Promised Messiah ^as wrote:

As some of the Jews had accepted Buddhism, there was no alternative for this true prophet ( Jesus ^as) but to turn his attention to the followers of Buddhism. As the Buddhist priests of that country were waiting for the “Messiah Buddha” to appear, they hailed Jesus as the Buddha… It was indeed a blessing for the followers of the Buddhist faith that he ( Jesus ^as) stayed among them for quite some time and they came to have a good knowledge of the facts of his life and of his noble teachings.

(Jesus in India, p. 87, 90)

However, the fact that they preached to non-Israelites does not mean that they were universal prophets. When Hadrat ‘Isa ^as is mentioned as a Prophet sent to the Children of Israel, it means that his teachings were primarily for the needs of his people in his time, although other peoples who he happened to encountered could still benefit from his light. Hadrat Khalifatul-Masih IV ^rta explained that when The Promised Messiah ^as lays stress on the fact that Jesus was not for the whole world but only for Israelites, it does not mean that no one else could accept his message. What he means is that the main purpose of his coming, like the earlier prophets than him, was to a certain people. None of the earlier prophets was universal. We argue against their universality; we do not argue that anyone else living in the same region was not meant to accept him (Question Answer Session, Jan 18, 1986).

Hadrat Khalifatul-Masih IV ^rta said:

Verily, no one before the Holy Prophet of Islam had beckoned the whole of humanity, and no book before the Holy Quran had addressed the entire world. The first such claim was made in favour of the Holy Prophet of Islam in these word:

And We have not sent thee but as a bearer of glad tidings and a Warner of all mankind, but most men know not (Surah Saba’, 34:29).

And then:

Say “O mankind, truly I am a Messenger to you all” (Surah al-A‘raf, 7:159).

(Some Distinctive Features of Islam, p. 6)