Fortune favors the prepared mind.
Troop's AI is something that can be studied. We do not understand all of it but 99% of them time, good attackers can predict their troop's behavior because they've been observing them over and over and over. Also, good attackers have plan B, so when things are not going as expect, they switch plans on the fly and could still succeed. Do skilled players need luck? Of course they do. Hell, everybody does. Skilled players, however, don't rely on it as much to succeed YET a bit of luck could take them a long way. A ton of luck, on the other hand, might not be enough for someone who is completely clueless. Luck favors you more when you have a good plan and execute them well. All you need is to not screwed over by bad luck. When you have no plan...well then luck plays a big part because that's all you have to rely on.

