Claudio, like so many Shakespearean romantics, brings a full heart of optimism and a certain degree of naiveté to the play, both of which ultimately lead to conflict, complications, and chaos. The speed with which he and Hero meet and fall head-over-heels in love paves the road for Don John’s schemes, many of which are fueled by the fact that Claudio is only too willing to believe the worst and fan the flames of the burgeoning conflict. When Don John stages Hero’s affair by using Borachio and Margaret, Claudio doesn’t merely call off the wedding; he publicly humiliates Hero and leaves her at the altar. His vow to besmirch her name, much like the quickness with which he initially believes Don Pedro must be flirting with her, is a reflection of the opinions of those around him, suggesting Claudio is not just quick to despair but also very malleable, unable to think for himself. That Claudio doesn’t even consider that Don John might be lying supports this—he is either susceptible to persuasion, extremely idealistic, or both. He falls in love with Hero swiftly and passionately, and he falls out of love with her with a similar intensity. He doesn’t pause to think critically about his situation, opting instead for a scorched-earth strategy that leaves him burned as well.
Though Leonato tasking Claudio to marry his niece as “punishment” for Hero’s supposed death is a ruse, it is notable that, even in his grief, Claudio readily accepts a new bride. Though we might view this readiness as contrition, a means of penance for his past sins, this willingness to blindly marry a stranger at the behest of Leonato only serves to further support the notion that Claudio is easily led at best, and lacks moral convictions at worst.