Laertes must be losing in this fight because why else would the king want it broken up?
Like – I know he has a plan – but what if Laertes could just take care of Hamlet for him right then?
I suppose it’s a political choice.
He can’t appear to be allowing violence before him – in a woman’s grave, no less.
Also. Pluck them asunder is such a delightful turn of phrase. It’s one of those that, even if you don’t immediately know what “asunder” means or what plucking might have to do with anything, you can work out the sense in context. It’s the kind of phrase I can get a middle school boy who hates English class to get into.