The latter part is abbreviated, hoping the readers may guess it.
The Japanese language often adopt this kind of abbreviation, the rhetorical effect of which resembles, I suppose, indirect/modest/vaguely-spoken expressions.
For this reason, you may think to use "it seems that," "I think/thought," "would," or something like that.
My attempt: It seems that the more I did research on this question, the more difficult conundrum it would have become.
(when the 問題 was a math question)
It seems that the more I did research on this matter, the more difficult it would have become.