After jack and algernon’s lies are revealed, how does wilde use triviality to keep the play from becoming too “serious”?

Wilde is the master of satire and triviality, for good reason. At the end, when all is revealed, he keeps things lighthearted by continuing the jokes, so to speak. Instead of showing the women getting angry, he shows them scheming how to go from there before teasing them and forgiving them. Let us also not forget the entrance of Lady Bracknell, who while imposing, does present an interesting relief from trivialities. Because she's so serious about things, she's comical because you can't take her seriously. She's just one other ridiculous character in a ridiculous play.

She is smart because she left a trail