IDK what their 2018 pay increase was. But like most, I doubt it was all from day 1. Probably X% over the years. So, I kind of get that it's been 6 years and they want more cause cost of living went up since then. But this all depens on what they're currently making.
I would say the biggest concern is the automation. Like the auto industry where much is automated compared to decades ago, maybe they see the writing on the wall. With cars, it didn't happen over night. But small innovations here and there in the name of safety. Then add in more and more and next thing you know, robots are building cars.
Example concept: Porsche acid dips the entire frame of their cars for rust proofing. I can image in the 60's it probably took 20 guys holding it to do it or they did it 1 portion at a time. Then they began using lifts, so now you need say 4 guys to just attach the lift to the frame spots. Now the robot grabs the entire frame and does the process. Keeps workers from fumes and getting splashed. Using muscles to hold the parts, etc...
Seen vids in China about the crane operators all in an office operating it remotely. About 12 computer set ups and joysticks. Compare that to here where it's a guy sitting up in the crane.