could understand why Objective-C is a thing
Objective C is what happens when you let Steve Jobs come back to run your company.
Pre-OSX, the Mac used antiquated but still sensible C programming interfaces (the antiquated part was that it was designed prior to Macs having MMUs, so they had a lot of double-indirection nonsense going on). When they brought Steve Jobs back from the dead to run Apple again, he brought a lot of the NeXTStep people with him, and they had gone all-in on Objective C (as far as I know, they were the only ones). I have no idea what they thought was so great about it, but I guess they were SmallTalk fans or something.
So when they replaced the antiquated pre-X Mac OS with X, it was all NeXTStep-styled throughout. Unix at the core, Objective C as the interface layer, etc.
And that's how we ended up with the huge pile that is the Mac OS X interface. The hilarious part is apparently they weren't satisfied with having one ridiculous language that nobody else uses, so they added SWIFT, and now they have two :(