"Да" introduction particle. In this case it can be traslated as "And..." or just omitted.
"всё" before verb can be translated as "all the time". That is action of verb lasts long period of time.
"думал"="thought"
"видней" literally = "to have better view". second meaning "to have better knowledge of situation".
"наверху" literally = "on the top". in this context meaning is "upper levels of governance/authority". boss/director/minister/president and so on.

That is "But he thought all the time that government knows better what to do".