Notice the tense shift built into this text. Isaiah describes a future feast, future destruction of death, future wiped tears, and then jumps to what people will say once it happens: surely this is our God, we trusted in him, and he saved us. The declaration comes after the trusting, not instead of it. The people in this text spent time simply trusting before they got to say surely with confidence. And what finally gets swallowed up isn't described modestly. Death itself, the thing every other fear in life is downstream from, gone, not managed, not made bearable, actually swallowed.