It’s a surprising move, especially after Rooney left Aberdeen for Salford for more money - I’d expect Hearts and Aberdeen to have similar budgets, but maybe he has gone in hope of getting regular football, maybe challenge for Europe or a cup? He’s still young, it’s not a great league technically but it’s aggressive and he’s still young enough to use it as a stepping stone - I hope he does well.
As good as he was for us and the potential he showed, being linked to top English Premier League clubs was probably a bit flattering and above his ability in my opinion.