Greener Than You Think by Ward Moore.

It's a satirical science fiction novel written in the 40s that, aside from the dated cultural references, might've been written today.

The MC and narrator is a salesman who answers an ad wanting someone to market a product that will make it so that plants can extract nutrients from virtually anything. The woman who created it envisions people in even the most barren areas being able to grow food regardless of the quality of their soil, but the MC believes that she's just a dumb woman who doesn't understand business, and obviously those people couldn't afford to pay enough for this product, so the better idea is to market it to suburban homeowners to put on their grass.

Which leads directly to the entire world being overrun by an unstoppable mutant strain of bermuda grass.

Throughout the entire chain of events, the MC remains completely oblivious to the threat facing humanity, and is instead entirely focused on profiting off the events. He's like every self-absorbed politician or corporate executive rolled into one, overtly bringing destruction to countless people in his blind pursuit of profit and privilege, and railing against anyone or anything that stands in his way.

And naturally, the people he meets pretty much universally loathe and detest him. And if he notices it at all, he ascribes it to their purported jealousy or envy or ignorance.