TSAN though is the arguably Far more important between the two, though Asan is
also important ofc.
It spots data-races. You know how sometimes programs or systems just crash,
but only under very specific random circumstances because sometimes one thread
does something at just the right time to murder another thread?
Those are data-races.

TSAN tries to spot those. Or more exactly, it tries to spot where 2 threads
access the same piece of memory without that piece of memory being secured by a
lock or some other mechanism that prevents one thread blowing the legs off from
another.