Bonjour Ted,

Copied from the lesson:-

"Whereas in English, you will need to use a subject pronoun after than (... than I (do), you (do), he/she (does)...), in French you will once again use the stress pronoun after que (... que moi, toi, lui/elle, nous, vous, eux/elles). You will also never repeat the verb with (do/am/have) afterwards."

The above is why I see your text as needing to be written  "Il est aussi riche qu'eux" with "eux" being the stress pronoun.

Bonne journée

Jim