The Hamlet Project

I have a LOT of questions about this pirate attack. I mean – the pirates boarded the ship that was going from Denmark to England. Hamlet hopped on board the pirate ship while the pirates were fighting with the Danes. Now – why would the pirates get on board the Danish ship, fight everyone on it and then leave the Danes to go on their merry way to England?
Like, if they got control of the ship to get on it, wouldn’t they take possession of it? Or kill some folks on board? I suppose they could have just taken all the goods but the most likely scenario seems to me to be that this entire pirate attack was a set up. How else would Hamlet know that Rosencrantz and Guildenstern are holding their course to England? If he’s hiding out on a pirate ship – how would he know what the other ship is doing? We don’t get to see any of these pirates – but I would very much like to, I would watch a play about Hamlet and The Pirates.