Nobody knows why he didn’t start, but I have a theory:
if Lewis starts, then the team has no viable options off the bench to give itself a boost - Wallace is admitting we’re parking the bus and TMac is a liability of not knowing how the other team will take advantage of the loss of effort. But if Lewis is on the bench, then Dome has a card he can play to alter the tactics.
It’s like, if you can start a match with a slightly subpar lineup and either hold or take a lead, then you have the ability to do many things with quality sub(s). Whereas if you blow your wad with your best players starting and they don’t break through, you’re then suffering from potential negative sub options.