Why are scout drones so large in relative size?

I should not be able to see this drone.

since they are not visible to search radars, i believe its for spotting purposes but yeah it shouldn’t be bigger than a helicopter.

When drones were first created they were huge in comparison of today’s drones. Batteries and the equipment on board were a big factor for them. These days, the military has been able to shrink a lot which can make the drones smaller but just as or better than capable than the drones of old.