Tighten up Motivation section

Co-authored-by: Adam Turner <9087854+AA-Turner@users.noreply.github.com>

Author: zklaus

peps/pep-0780.rst

@@ -36,12 +36,12 @@ new marker variable, ``sys_abi_features``.
 Motivation
 ==========
 
-:pep:`508` established environment markers to specify dependencies based on
-environment conditions. Since its adoption in 2015, the Python ecosystem has
-evolved and new features warrant their own environment markers.
-
-The primary motivation for extending the allowed set of environment markers now
-is free-threaded CPython [#python-free-threading]_ emerging. Currently there is
+In 2015, :pep:`508` established environment markers to specify dependencies
+based on environment conditions.
+The development of free-threaded CPython [#python-free-threading]_
+has underlined the need for an environment marker to discriminate between
+different ABI features that the interpreter was built with.
+For example, currently there is
 no way to distinguish between a GIL-enabled and a free-threaded CPython
 interpreter with an environment marker. This leads to real world issues for the
 adoption of free-threading and its incremental rollout. When a Python package