Earlier quoted context omitted.
I don't think there's any issue monetizing a chronological timeline. The issue for them I imagine is retention: with chronological, it's likely that when you visit Twitter the first few messages you see are not interesting and you leave. But if they put a tweet that's popular among your social group in front of you? Odds are that's interesting to you and you stick around a bit longer. I dislike that, to be clear, but…
With reverse chronological timeline, it's harder to build a advertising profile. While it's important to know what tweets a user is interacting with, the personalization option can surface more things as "You might like", "You follow x, and he liked", "Interesting tweet on the topics you follow/might like" and so on. Whether or not you choose to interact with anyone or more of those is a signal, and helps with advert…
Whether or not they show topic data for a particular tweet, they generally have it. I only use the chronological timeline, and I cleared out the interests list a year or two back, but they have built up a profile of hundreds of interests for me.
I suspect forcing the ranked timeline on people is all about a small portion of Twitter juicing their engagement metrics, with no grand cross-team strategy in play.