What is "actively used"? The bash session that I was using 2 seconds before system grinded to a halt sure didn't count.

The set of possibly blocking operations for interactively using bash is big. Executable pages of the bash executable are far from the only thing that could be missing.

If the machine is swap trashing, all i/o goes to the same congested queue. .bash_history read or write access, memory allocation, stuff your terminal program does, stuff your wayland compositor or X11 stack does, bash accessing data in its memory that has been swapped out, etc etc. And each of those could be waiting for a while to issue their IO request since the IO system is flooded by swap IO.

There should be a tool that can show the interdependent graph of pending, blocking io operations.

Your bash session is most likely still in memory but the system is spending 99.9% of time waiting for swap I/O, trying to free a few pages of memory. Swap random access latency is 10^3 slower than RAM.