Why did Vikings raid towns instead of establishing settlements and conquering the land?
Vikings did settle and establish settlements. Dublin and Cork in Ireland for example. Normandy in France was populated by Northmen or Normen. Swedish Vikings founded the cities of Novgorod and Kyiv in Russia and Ukraine. Vikings were far more than rapists and murderers, although they did do a lot of that as well.
What weapons were popular with Vikings during raids? Did they ever use siege engines? What kind of armor was commonly worn?
For weapons, spears and axes were the most common melee weapons and bows were also likely used as well. Some wealthy Vikings used highly sought after steel swords, and every Viking likely had a seax dagger to fall back on as a last resort. As for armor, the most common type was chain mail, a steel helmet, and a heavy shield.