Realistically, the blame lies less on Wilfried than on Veronica and Sylvester, who raised him poorly.

Well, they didn’t raise him at all. That’s the problem.

From Part3, Volume 5:

The plot was fairly devious, if you asked me: Wilfried had essentially been raised by his grandmother since birth, so it only made sense that he would love her more and consider her more trustworthy than his actual mother, who had only recently been given the opportunity to regularly interact with him. Veronica had his unconditional trust, and it stood to reason that he would welcome her guidance in a situation like this.

Letting him run free around nobles of all factions? Ridiculous. Oswald should have been instantly fired for allowing this to happen, at the very least.

Oswald did have his eyes on him until he was relieved by Linhardt.

“Nothing abnormal happened while I was there,” Oswald responded, “and I stayed with him until Linhardt came to relieve me.”

Linhardt had desperately run around trying to keep up with Wilfried and his friends, but at one point, he tripped over and fell hard enough to hurt his legs. While Linhardt was being treated, Wilfried was looked after by his friends’ attendants.

It’s not being said specifically, but I assume that tripping Linhardt was also part of the plan to get Wilfried out form under his attendants eyes. I have enough problems with Oswald as a retainer for Wilfried, but in this case he’s blameless for once.