Why does my component only update in a dummy For loop?

The component works correctly in the For loop, but doesn't do anything on it's own.

<For each={[props.string]}>
  {(t) => <Item content={t} />}
</For>

<For each={[props.string]}>
  {(t) => <Item content={t} />}
</For>

<Item content={props.string} />

<Item content={props.string} />

The component itself doesn't seem to matter, it can be as simple as

return props.content

return props.content