What: Freeport-McMoRan's (NYSE:FCX) shares fell just over 17% last month. That conluded a year in which the mining and oil company saw its shares fall a painful 70%. 

So what: The big news in late December was that the company's co-founder and chairman of the board, James Moffett, was stepping down. However, that news came out on December 28, well after the monthly damage had been done. In fact, the shares barely moved on the announcement.

That's is why the year-long decline is so important. Freeport's drop has a lot more to do with the continuing troubles of the company's ill-timed foray into oil than a leadership shift. To be sure, Moffett had a big hand in that oil decision, so there's a reason he's stepping back from his board role. This, by the way, is roughly similar to the playbook activist investor Carl Icahn has been using at Chesapeake Energy (NYSE:CHK), another investment in which he seemingly orchestrated a big management shake-up. But the impact of Freeport's oil shift was the real reason for the December decline, and that lingering pain was on clear display earlier in the month.

So, what happened? To start, Freeport announced on December 9, 2015 that it was again reviewing its oil business for places to make cuts, it was further trimming its spending in its core copper arena, and (here's the kicker) it eliminated its dividend. Adding insult to injury, Freeport had to amend the terms of its credit facility to give it more breathing room -- it's heavy debt load is a direct result of its shift into oil. No wonder investors were in a selling mood last month.

Now what: Freeport-McMoRan's mining operations are under stress from low commodity prices, but they are pretty good assets. The oil business, however, has proven to be a very expensive mistake. At this point, there's no easy way to fix what ails the company. It's going to take time, a lot of hard work, and a rebound in the commodity markets -- notably oil.

Seeing Moffett step back may be a signal that the company is getting serious about righting the ship in 2016. But at this point, Freeport is really only appropriate for aggressive investors with a contrarian bent.