Or HaChaim on Genesis 9:3/אור החיים על בראשית ט׳:ג׳

1 כל רמש אשר הוא חי, Any moving thing which is alive, etc. We need to understand why meat had not been permitted as food to Adam whereas now G'd permitted Noach to enjoy a meat diet. There may have been three reasons why Noach was permitted to eat meat. 1) His care for the animals during a whole year in the ark kept the whole species alive. 2) He expended a great deal of tender care on these animals. It is with regard to this that the Psalmist 128,2 says: יגיע כפיך כי תאכל אשריך וטוב לך. "When you eat what you have laboured for with your hands, you will be happy and well off." 3) G'd was in a favourable frame of mind having promised not to destroy all flesh. Hence He permitted Noach to eat of the fruit of his labours.