Why did they save the best character until so far into the shown

lewd

Can somebody explain me:
>gem whose only meaning is amusement
>6000 years in isolation and literally standing still
>transforms without having been poof'd
>somehow has access to a device that can suck a planet dry
>also access to a scythe that "resets" gems
>manages to defeat three gems that have been fighting for thousands of years (but they're "rusty" after being in peaace for like what? 3 years?)
This is utter bullshit.