First, a high degree of impunity for far-right vigilantes in Israel is nothing new. If you are familiar with the "price tag" attacks and all-out rampages against Palestinian villages, what we're seeing with the blocking and looting of aid should be unsurprising. Over decades, Netanyahu and others have occasionally denounced some of this, but relatively few arrests are ever made when compared with the extent of the violence. Even when settlers attack the IDF itself, that is largely tolerated.
Second, since the current war on Gaza began, Israeli policy has all but explicitly been to do as much as possible to prevent aid from reaching Gaza without directly banning it all, citing security concerns. Israel refuses to facilitate safetysafe aid delivery through normal means, which as led to this absurd scheme with the floating piers. Allowing vigilantes to disrupt aid deliveries is consistent with that pattern of disallowing aid while maintaining plausible deniability.