I distinctly remember their experiments with inlining ads "ethically", and all the discussion about that by outsiders, and how the "ethically" part quietly went away and they settled on "clearly trying to trick people". I have no inside knowledge but can only speculate that those early experiments shot the profitability arrow
so hard upward, and that every tweak making the results more deceptive did so
even more, that they just couldn't resist becoming... well, what they became after that. And nearly all the difference between their numbers before and after those tweaks are, plainly, due to deception.
[EDIT] also and again directly related to their inlining of ads with search results, I've noticed a trend even among the reasonably tech-savvy to click an ad that is what they wanted... even when the natural result is just a couple entries under it. That's not sending people to the wrong place but it is gaining Google money from something that is exactly and entirely rent-seeking, as in it could go in an encyclopedia as a perfect and unequivocal real-world example.