yitzchokm:
The comment before yours guides you to search the prior posts on this subject. Do so.
I will only repeat a strong rebuke. Reb Moshe ZT”L NEVER said it was muttar, and it is dishonest and unfair to claim he did. Review his teshuvos about it. Never a heter.
His children were consulted about Reb Moshe’s teshuvah on this subject. They stated unequivocally that his absence of declaring an issur was based on the minimal evidence at that time about the dangers of smoking. By now, it would have been way beyond the criteria needed to make an issur.
What is remarkable is that the ones looking to pronounce a heter are the ones who smoke and don’t wish to stop. Nearly all gedolim who smoked stopped, and the roster of those who proclaim it as an issur d’oraysa is quite long. See earlier threads on this.