kernel_task takes a lot of memory

It is normal for kernel_task to show those values. This is not something that is a "problem" in any sense, or makes your system slow or anything like that.

The 71.2 GB of virtual memory is indeed virtual - so it doesn't (necessarily) have anything to do with actual memory being used. Your computer most probably has a 64-bit CPU capable of adressing huge amounts of virtual memory.

Usually Intel-based computer have operating systems that limit actual virtual memory usage to either 48 bits or 57 bits. In your case the 71.2 GB of virtual corresponds to just over 36 bits. I.e. it is really nothing - about 0.02% percent of the virtual memory available to the system.