The problem was the gameplan was built around Armstrong who left after 1 series.
I expect Kyren Williams will have a much bigger role now that Armstrong is out for a while as he is the only other guy that brings a similar skillset with his receiving abilities. He probably got very few reps leading up to UL (as would be expected with a 4th string player) so the coaches weren't comfortable throwing him in there. With plenty of practice time, he'll be ready and will mitigate Armstrong's absence moving forward.