Strategy wise I get where he is coming from. Leave the weaker members at the somewhat safer location with the supplies while the stronger members scout the dangerous areas ahead.
The only tactical error -- not setting up a second-in-command that everyone trusted. Which is saddening.
He either got too impatient and made a move. Or He came to the understanding that these girls are hindering progress and made a hard choice.
But I still don't blame him for sneaking out, absolutely no one was going to voluntarily let him go. Those girls know they bring little to no help to the table, aside stress relief.
Anyway, I hope the girls will trust him to comeback later and just wait while doing their best. Can't wait to see what new girl is all about though. Definitely skilled, but how skilled and why is the question.