Bangladesh won because they perform well both in batting and bowling. Fielding is not that much important as it is in ODI or T20I except the fact you need to be good in taking catches at slip position or near batsmen. NZ know how important second test match will be and they will try to win the match to draw the series. The last test series between both these countries played in NZ also ended in draw 1-1.
I can't fully agree with that fielding is not much important as like ODI and t20 format. Because I think batting and bowling play an important role in the game of cricket as well as in fielding because there are so many records above the catches in the fielding that there are many important wickets to drop catches and they become a threat to win after getting a chance.
You are right in your thinking as test match depends on wicket so good field plays a big role in run out and cash out. Overs are not a problem in Test matches because here wickets can be played all day so it is more important for the opposition to bowl and field well to take quick wickets and prevent them from scoring big runs like four & six. And if the batsmen can stay on the field for a long time and don't miss single runs then they will be able to collect a lot of runs which should be at least 300+.