Confused about how the same weight looks different on different people

For context, I am 26F, 5'6 and 67kg. I am about 5-6 kg overweight and working towards reducing it. I have good muscle mass. Not ripped or anything but a decent amount of muscle. But I see a lot of people on here, who are the same or lesser weight than me, who look a lot fatter (not fat-shaming, just an observation).

And on the other extreme, I see very very muscley guys, who actually weigh lesser than me. Shouldn't they weigh more than me given that muscle weighs more than fat? Why exactly do I weigh so much even though I don't really look like it?