It made good sense at the time.

Numbers 14

But Moses said, “Why now are you transgressing the command of the Lord, when that will not succeed? (v41)

This chapter is not a proud moment for Israel. Their complaining against God presumes a higher wisdom and a better purpose. Then, Moses asks the question that absolutely has to be asked (and asked of us). This is not about some quest for self-righteousness in order to make God unnecessary. This is not about a set of rules laid out as some sort of twisted test...like God is playing MouseTrap and we're trying not to get caught.

Why are you sinning when it doesn't work?

It doesn't make God unnecessary - it makes him, if anything, more necessary. It doesn't display higher wisdom or better purpose. It is folly. You don't have to be on a quest for your own righteousness to work for obedience. Those quests end poorly. At some point, you look up and realize that obedience is the only thing that makes sense.