Good idea, but clearly, no one took it seriously

While I love the idea, it is very clear from Challenge #1 that something is wrong: absolutely no one has respected the initial instruction of the challenge:

Imagine you were talking to a baby. You would probably modify your speech to make it more engaging and accessible.

I have checked every single entry. All of them are either a hardcoded dictionary that changes common words into the same word but with additional "w" (I have actually counted 18 out of 45 entries that change "hello" into "hewwo". How original.), LLMs, or duplicated syllabes / replaced letters.

The challenge was to turn YOUR (as an adult) speech into something a baby can understand. Not turning a wall of text into what a baby would say (emphasis mine):

Baby talk is a pattern of language used when adults talk to babies.

Not when babies talk to adults. Unless you say "Hewwo" to your baby, which I hope you don't, since improperly talking to your baby can lead your baby to then talk improperly and struggle to pronounce words correctly.

I expected to see entries that would do thinks like substituting complex or uncommon formulations and words with more common ones ("said he" -> "he said", "enquired" -> "asked", ...) with highly clever tricks to detect english speech patterns programatically.

I feel like everyone took the challenge as a joke and tried to be funny. It turned from a coding challenge to a joke challenge.

Here are, in my opinion, the reasons why this happened.

Small time windows can lead to low effort and lack of originality

One week is a very short amount of time. Many of us have a job and might not have enough energy or motivation to do coding challenges during week days because of that, making week-ends or off-days the only timeframe to work on such a challenge.

This essentially reduces coding time from 7 days to 2 days for many, many people, which is not enough to make something good.

This also encourages looking at what others have done instead of coming up with an idea, because finding something original is often the most time-consumming thing in a programming project.

Maybe give us 2/3 weeks?

Lack of downvotes

Since you can't downvote an entry, people who think entries are funny (no matter if they are actually as the instructions asked nor if they employ clever programming techniques) will upvote. People who would have prefered more serious entries can only stay neutral, they can't even upvote serious entries since there aren't any.

Entries visibility

I see you tried to keep it fair by having other entires hidden for the first half of the timeframe. Considering the challenge started on a Tuesday, this means that entries were visible by the week-end when people usually have more time to work on this kind of things.

Entries are (by default) sorted by how upvoted they were, and all put on a single page. This should be randomized, as having the most upvoted one on top will just make it receive more upvotes naturally that whichever entry was just posted and has no upvotes.

Entries should be, in my opinion, hidden for the whole duration of the challenge, and then followed by a week-long voting phase (like moderator elections) where they would be displayed randomly to each user.

Give example on what the objective may be

You gave sample text to translate, but I believe the objective of the contest would have better been understood if you provided a sample translation for those too, just as an example of what you meant by "modify[ing] your speech to make it more engaging and accessible".

Participants, please, don't forget: serious can be funny, too!

Something that needs to be reminded is that coding challenges can be just as funny as joke challenges.

It is entertaining to write a program that performs an interesting task, documenting yourself about it, think of solutions, etc. It doesn't have to be a "hello" to "hewwo" dictionary to be funny.

Yes, challenges are meant to have fun, but you wouldn't use a car in a running contest, even if it'd be funny to look at, would you?

Conclusion

I feel like Challenge #2 is a much better approach and less prone to misinterpretation, but many of the points raised in this answer still stand.