What's up at the TIOBE Index? Surprisingly, Objective-C

When Apple introduced Swift, Objective-C quickly dropped down from its number 3 spot in the TIOBE index. Way down. And it certainly seemed obvious that from that day on, this was the only direction it would ever go.

Imagine my surprise when I looked earlier this March and found it back up, no, not in the lofty heights it used to occupy, but at least in tenth place (up from 14th a year earlier), and actually surpassing Swift again, which dropped by almost half in its percent rating and from 12th to 17th place in the rankings.

What's going on here?