Sweet Home was a case about habitat destruction where SCOTUS interpreted "take" in the Endangered Species Act forms of "harm" to include not just a direct application of force like hunting, but also other acts or omissions that affect the listed species like logging. IIRC there was a Chevron analysis where the enforcing Agency's interpretation of "take" was found reasonable and thus given broad discretion, though I'm not sure they actually went through the steps in the decision. Also some regular statutory interpretation, maybe noscitur a sociis? But mostly I think just in order not to frustrate the purpose of the ESA, they needed to allow the DOI to include harms that might not be proximately caused by, or foreseeable results of, a particular action. It's about agency discretion and policy making. See Babbitt v. Sweet Home, 515 U.S. 687 (1995); see also Chevron inc. v. NRDC 467 U.S. 837 (1984).