You're comparing a kernel with an entire operating system.

Your numbers don't check out, please provide sources. The Linux Kernel has around 40 million lines, the OpenBSD kernel around 7. You might have mistakenly counted OpenBSD/NetBSD as a whole system (the base installation), instead of solely the kernel.

Given BSD is supposed to be a complete package while Linux has a separate kernel and userland, that's probably part of why.

Doesn't mean anything. Lines of Code is a stupid metric because it's just an absolute count. Not relative to any implemented functions, not imaging the actual density. Especially stupid because you can easily tweak the count by bloating a function.

You're probabry including ports/ which contains all the software available for the platform

Is that more than the kernel? How much more?

One reason is that the coreutils in Linux use a lot of hacky or hard to read tricks to improve performance. OpenBSD explicitly wanted to make their source code more legible. FWIW I prefer the Linux approach.

This is why I typically refer to it as GNU+Linux and not just Linux. Two different and incompatible operating systems can use the same kernel just look at Android and GNU+Linux. Each of the BSDs is a complete operating system (userland + kernel).