Why to get into Israel, you need to renounce the Orthodox faith?
Of course, there is freedom of religion within Israel. But when you are a potential repatriate, the state is interested in citizens who do not pose a possible threat to Judaism. At the same time, as can be seen from the explanation of the author of the question, no one digs deeply and does not conduct a total check whether the person trying to move to Israel for permanent residence told the truth.
But if a person stubbornly stands on the fact that he believes in God according to the canons of another religion and does not intend to give it up even on paper and when asked about religion he is not ready to hide his real faith - “what, then,” the officials responsible for the extradition decide permits for repatriation, most of whom are followers of Judaism, "let them continue to believe in their own way, but on the territory of their state." After all, those whose ancestors were people who adhered to the Jewish faith have the right to permanent residence, although the Law of Return sounds a little differently (there is a special conversation about the inhabitants of the USSR, Judaism was etched out of their lives by all means).
The law of the State of Israel does not provide for the return of Jews of other religions. More precisely idolaters. This is how Judaism defines all man-made religions. Buddhism or Orthodoxy does not matter much