Just being corpsey? What the fuck does that mean? You mean it was intentionally playing possum and knew when to pop up to cause the most damage? Bullshit! Thus far the wights have given no indication that they're capable of reasoning to that degree. Or to any degree. They can't use tools other than clumsily swinging swinging swords, they don't work together, they don't ambush, they don't move or think tactically in any way even when in close proximity to a White Walker.
Given what we know about the wights, "Yo, you guys lay there until the nights watch takes you inside, then animate yourself and attack" is far less likely than giving the White Walkers the ability to time-delay re-animation.
Except that I already pointed it out TWICE. The wight remembered where Mormont slept. Others were left dormant outside of the Ice Cave where Brand spent all of last season. They were there under the ice for God-knows how long and emerged as soon as Brand arrived.
You are also forgetting that they were clearly receiving direction from the Night King and other White Walkers at Hardhome. They were directed off cliffs, they were directed toward the gates, they were directed to stand on the shore... heck: they out-right show a White Walker on a zombie horse directing them south at the end of an earlier season.
Every indication is that they do have at least some capacity to be directed and to perform tasks given to them. How you could come to the exact opposite conclusion and claim "no indication" baffles me. It's pretty firmly established.
Literally everything you said wasn't true. You admit that they use tools (swords and shields) but counter that they don't work together despite them forming an army and taking down a gate. You said that they don't ambush even though we already saw them do that at the ice cave. There was DEFINITELY a tactic when it came to assassinating Mormont.
Granted, all of these things were directed by the White Walkers and their magic, but that's exactly what we argued that the wights were capable of: executing directives under the influence of the White Walkers. They don't just turn and act autonomously.
If it was just a time-delay and the corpse was mindless it would not have known where to go to find Mormont and the wights outside of the ice cave would not have just happened to emerge from their resting places in the ground at the exact time there were visitors.