I doubt anyone would argue that Lam still has a lot to do to impress, but maybe this is reflected in the fact that he's only got an extra year.
I'm not sure how long it takes to source, sign and bring over a top coach, but I suspect that would have been very difficult in time for 2020 given that we owed Lammy at least a few months to try and turn things around this year.
If we'd reached July and Wigan were still near the bottom, the decision would have been easier - the 'find a new coach' ball would probably have started rolling by now. However, we're not at the top of the tree either, so giving him a one-year deal would seem like a reasonable response.