Why was the pike the rebels' chosen weapon, especially considering that they were facing soldiers armed with guns? There are two main reasons. One is that pikes could be mass-produced quickly and cheaply. The other is that government-approved militia units such as Fencible regiments were frequently armed with pikes because the government couldn't afford or didn't choose to pay for them to be armed with more serious weapons. The result of this was that the pike was already closely associated with the citizen soldier, and there were numerous men trained in its use who could be recruited to train the rebels.
Of course, none of these rebellions actually achieved their aims, but the tradition they started endured for a long time. The pike-wielding United Irishmen of 1798 inspired the Fenian Brotherhood of the nineteenth century, who became the Irish Republican Brotherhood and then the Irish Republican Army. Of course, Irish revolutionaries no longer go to war carrying pikes, but they do still sing this song.