Rav Moshe addresses the newly built Flatbush eruv that he hadn’t wanted to get involved in the project because there is many opinions on what is reshus harrabim and what is dalsos neulos and they can always consult the seforim instead of him. But once it was publicized that Rav Moshe was the one who permitted the eruv because of the previous sentence, he felt compelled to respond with his personal opinion as it was already laid out in his first teshuva.
Rav Moshe is trying to make five public points:
1) There is rational for an eruv in Flatbush.
2) The reasoning is evident in the seforim.
3) It is not Rav Moshe’s opinion to put an eruv in Flatbush.
4) Rav Moshe’s own opinion is clear from his first teshuvah.
5) People have difficulty reconciling 1 and 2 with 3 and 4.
This really is the whole story. Rav Moshe saw that people are misinterpreting what he he clearly wrote and said, and responded just to refute what they were stating in his name.
The debates that follow to our day are not really about halachah. The center of the debate since the late Seventies was, is Rav Moshe entitled to his opinion. Rav Moshe himself held he was, but others would say that the majority disagreed with him. And even Rav Moshe himself may have agreed that he wasn’t entitled to his own opinion.
Rav Shmuel Birnbaum was very bothered by this attitude. But not everybody should be a masmid like Rav Shmuel Birnbaum. He was enough for the whole Flatbush.
All the more so, to imagine what Rav Moshe was up against forty years ago, when rabbis still spoke about business acumen as a qualification for being considered an educated Jew.