Clark believed Lex Luthor was exactly that kind of person. So, when Lex learned about The Serpent of Phryne, his first reaction was not to verify it, but to concoct conspiracy theories around it. That was why he had so readily accepted Schiller's ancient Egyptian mythology explanation earlier: his imagination had already run wild.
Then, once Schiller confirmed his speculation, things became even worse. In Lex's mind, the matter skipped countless stages of development and went straight to the worst possible outcome: aliens had already spread across the entire planet, and if he did not do something, the world would be destroyed.
So he began doing everything in his power to resist aliens like Clark.
If things had truly been as Lex imagined, then his response would indeed have been swift. But the problem was that he had devoted all his energy to directly dealing with his own speculation, without ever verifying whether reality was actually what he thought it was.
Many people had this bad habit. First came anxiety. Upon hearing something vague and uncertain that seemed harmful to them, they became overwhelmingly anxious, as though some monster were chasing them from behind and they would die if they did not immediately find a solution.
So they poured all their energy into finding a solution, spent all their time imagining what they could do after reaching the worst possible conclusion, and even put those plans into practice as precautions.
But one crucial step was missing from all this: investigating what was actually going on.
Perhaps things were not that bad at all. Perhaps they were bad, but had nothing to do with you. Or perhaps they were bad and did concern you, but because there had been no investigation and vital information was missing, none of the contingency plans