The explanation is in the knowledge base
https://mariadb.com/kb/en/why-is-order-by-in-a-from-subquery-ignored/
But here it is, again: your ORDER BY clause is ignored by the optimizer. It is not a bug.
A "table" (and subquery in the FROM clause too) is — according to the SQL standard — an unordered set of rows. Rows in a table (or in a subquery in the FROM clause) do not come in any specific order. That's why the optimizer can ignore the ORDER BY clause that you have specified. In fact, SQL standard does not even allow the ORDER BY clause to appear in this subquery (we allow it, because ORDER BY ... LIMIT ... changes the result, the set of rows, not only their order).
You need to treat the subquery in the FROM clause, as a set of rows in some unspecified and undefined order, and put the ORDER BY on the top-level SELECT.