Bypass surgery does not fix blockages in the way stenting does, it simply bypasses them
with new grafts. Some blockages are not bypassed, for instance if they are not severe, or if the artery is small and does not supply a large area of the heart, or if the artery has no good runoff and is small distally. I am not sure why it was not done in your case, since I am not aware of all the details in your case.