Both endpoints failed, and the second one required subtle medical evaluations over Zoom during the pandemic. It was therefore doomed from the start, and increasing the number of participants would very likely not have helped. To add insult to injury, this second endpoint was only added after Anavex consulted with the FDA over the trial design. I do not blame Missling for this one; it's like blaming him for the pandemic and FDA feedback.
He does get blame for the overly compassionate trial design (even though we've been informed he's a sociopath) that put two thirds of the trial participants on the dosed arm -- which may have underpowered the placebo arm and likely influenced the placebo parents to mistakenly believe their daughters were on the drug.
It's at least an oversimplification, and perhaps an error, to say the trial design failed for lack of enrollees. We can at least agree that the Rett trial did not disqualify blarcamesine as a potential Rett therapy.