Why the rule cannot recognize the input ?

[ghost]

main = { expr+ ~ "ORDER BY" ~ EOI}
expr = { this ~ ("OR" ~ expr)* | other_thing }


this = { "this" | "DER" }
other_thing = { "this" }

WHITESPACE = _{ " " }

The input: "this ORDER BY"

 --> 1:12
  |
1 | this ORDER BY
  |            ^---
  |
  = expected expr

[ghost]

It fails when using the sub rule this ~ ("OR" ~ expr)* of expr , but it doesn't choose the second alternative other_thing which can parse "this" only, then parse "ORDER BY" using literal in main, it should be success.