Tolkien says nothing directly about this, so any answer is going to be in part speculation. (Perhaps informed speculation, but still!)
In the comments to the original question, OrangeDog and jo1storm are on the right track: Basically, Tolkien understood the nature of the scientist, the techie, the engineer, the craftsman. They all tend to be people who have fallen in love with their science or craft and tend to forget that anything else matters. (And also tend to forget that people are more complicated than craft.)
Beyond that it is very easy for creative people of any sort to take pride in what they have created -- this is often one of the main motivativations for creation. But it is perilous as even just pride in one's own skill can turn to envy of others' skill and into greed which hoards what that skill has created. Tolkien speaks directly to this in the Ainulindale:
...but the delight and pride of Aule is in the deed of making, and in the thing made, and neither in possession nor in his own mastery; wherefore he gives and hoards not, and is free from care, passing ever on to some new work.
and later:
[Aule] is a smith and a master of all crafts, and he delights in works of skill, however small, as much as in the mighty building of old. His are the gems that lie deep in the Earth and the gold that is fair in the hand, no less than the walls of the mountains and the basins of the sea. The Noldor learned most of him, and he was ever their friend. Melkor was jealous of him, for Aule was most like himself in thought and in powers; and there was long strife between them, in which Melkor ever marred or undid the works of Aule, and Aule grew weary in repairing the tumults and disorders of Melkor. Both, also, desired to make things of their own that should be new and unthought of by others, and delighted in the praise of their skill.
After Aule has created the Dwarves and been called on it by Eru, he says:
Then Aule answered 'I did not desire such lordship. I desired things other than I am, to love and to teach them, so that they too might perceive the beauty of Eä, which thou hast caused to be.
I think that Tolkien perceived a flaw in all creative people (himself doubtless included) which is particularly easy for people who build/create/invent physical things fall into: Wanting to hoard and control and rule and be Lord.
Aule was the best of Ainur of this type, and he very nearly fell when he created the Dwarves. Melkor, Sauron and Saruman did fall.
Melkor wanted to create, but he wanted to create his own universe and then to rule it. His pride in his own accomplishments led him to be jealous of his nearest competitor's works. Aule creates a people, Morgoth creates slaves.
Sauron and Saruman, lesser beings, fail in lesser but similar ways.
Among Elves, we see Feanor, of course:
The heart of Feanor was fast bound to these things that he himself had made.
and
For Feanor began to love the Silmarils with a greedy love, and grudged the sight of them to all save to his father and his seven sons; he seldom remembered now that the light within them was not his own.
In the end, I think that this pattern reflects Tolkien's own fear of falling due to over-involvement in his own creative powers. Perhaps one of the reasons he was able to invent such good villains is that he can see himself perhaps falling this same way.
But there's an additional point. Tolkien was uneasy with machinery and modernization and of all the kinds creative people, probably distrusts people who create physical things the most.
Treebeard says of Saruman:
He has a mind of metal and wheels; and he does not care for growing things, except as far as they serve him for the moment.
