Because that is incorrect. That would be 'Disfrutaron mucho de nuestra comida.
That English is very awkward. 'They enjoyed our food very much' would be better.
Couldn't it also be imperfect mood?
We don't know the context, and it could be that the children enjoyed our cooking. (for years) ... Si o No?
Yeah, sure, without context, the imperfect could be used here as well. The Spanish sentence seems to refer to just a single instance here.
Please note that the imperfect is not a different mood, just a different aspect.
- tense - relation between time of speech and time of action (past, present, future)
- aspect - temporal structure within the action (perfective, imperfective, progressive)
- mood - communicating the speaker's intentions or beliefs (indicative (statements), imperative (orders), subjunctive (hypotheticals), conditional)