I'm not going to ask the PL anything. I assume it wasn't logisitically possible to play the game the next day. You need to arrange policing and stewards for the game to go ahead and that can't be done at the drop of a hat, particularly with the prospect of further protests the next day.
Playing midweek might be fairly common but that's not the issue here. It's the lack of time for preparation and planning. If the West Brom - Liverpool game is to be moved, we're now 8 days away from when it might be moved and neither club still knows if that game will be played then. How are Liverpool and West Brom meant to plan their preparations for this weekends games when they don't know if they're going to have to play another game on Wednesday or not? There will be players that might be carrying injuries or fitness issues and can only play once in a week, how do they decide whether to play them on Saturday/Sunday, when they don't know when their next game is? If the plan is to move the West Brom game to next midweek then both Liverpool and West Brom have now been disadvantaged and through no fault of their own.