Unless they say he resigned then it's a safe bet that he was sacked because of the pay off you mention - no manager walks away from all that money.
As for whether it makes sense to do it now, I actually think it makes perfect sense. You have to remember we've got a WC this summer (not sure how many internationals WBA have got tbf) and we've got a shortened transfer window from this summer onwards so any new manager that takes over at the start of pre-season may only have a month or so to evaluate the players and then make the changes and signings he wants. West Brom are down and Pardew staying or going is not going to change that. West Brom have to decide on who is the right person to bring them back up next season and if that's not Pardew, which it obviously isn't, then make the change now and give the new manager the next 5-6 weeks to work with these players to help him plan for next season.
As for whether it makes sense to do it now, I actually think it makes perfect sense. You have to remember we've got a WC this summer (not sure how many internationals WBA have got tbf) and we've got a shortened transfer window from this summer onwards so any new manager that takes over at the start of pre-season may only have a month or so to evaluate the players and then make the changes and signings he wants. West Brom are down and Pardew staying or going is not going to change that. West Brom have to decide on who is the right person to bring them back up next season and if that's not Pardew, which it obviously isn't, then make the change now and give the new manager the next 5-6 weeks to work with these players to help him plan for next season.