I am the only enjoyer and the only lord of all sacrifices. But they do not know Me in truth, therefore they fall.

Clarification of the previous verse. The Lord is bhoktā — the ultimate enjoyer — and prabhu — the owner — of all yajñas.

Na tu mām abhijānanti tattvena — but they do not know Me in truth. Tattvena — in essence, in reality — not superficially. Through ignorance of this principle, cyavanti te — they fall, they regress.

Fall from what? From pure devotion, from complete understanding, from direct relationship. Worshipping demigods has temporary fruits, but does not liberate.