It's just that "manquer" is always followed by "de" in this context, and the combination of "manque de" and "de l'expérience" reduces to "manque d'expérience". (Because "de" is never followed by a partitive article.)

Using manquer (de) to say you/something miss or lack in French

Hi Frank,

"clearly lacks experience"   I've cut this section out of the text which I believe is why manquer is being used in that context.

Hope this helps

Jim