That particular set of verses is a total mish-mash of verses from other shanties. To make a shanty out of verses from several others was quite common, as the shantyman would sing whatever came into his head at the time. Thus, a new shanty was born.
The reference to hanging a man for making steam is very likely to have been a square rigged sailors dig at the new fangled steamships that were taking all their trade and spelling the death of "true seamen".
Donkey engines were generally seen as a good thing, which enabled sailing vessels to compete with more modern ships for some years to come.
As for the words not having to make sense, completely untrue.
They had to mean something to the men at work. To tell a story, to raise a smile, to lighten the heart and therefore to lighten the load of the job in hand. The rhythm was not necessarily in the verse, but more usually in the chorus where the men actually sweated on a rope, a capstan bar or pump handle etc.
The CHORUS didnt have to make sense, just be repetitive and easy to sing (shout in unison would be a better description).
The art of the shantyman was to be able to make up or remember verses at will, and to gauge the task with reference to the conditions prevailing at that moment, such as the fitness of the crew, the number available for it, the strength of wind, sea and tide, plus other factors too numerous to mention. (Or in my case, too difficult to comprehend to one who has never had to make a living at sea aboard a wind jammer.)

P.S. Mr McGrath of Harlow should be hung, drawn AND quartered.
Not purely because he suggested farting as a viable answer, but just because he should be anyway. So there !!!