Wherefore (dio). Not in the lxx, but it makes clear the argument in the Psalm.
I was displeased (prosōchthisa). First aorist active of prosochthizō, late compound for extreme anger and disgust. In N.T. only here and Heb 3:17.
Err (planōntai). Present middle indicative of planaō, to wander astray, common verb.
They did not know (ouk egnōsan). In spite of God’s works (erga) and loving patience the Israelites failed to understand God’s ways with them. Are we any better? They “cared not to take my road” (Moffatt).