Firebaes CNAME brought down website?

I am adding firebase authentication to a website, it was working well so I decided to get the domain verified to add some more functionality.

On the firebase documentation, it says you need to add two CNAME and two TXT records to the domain, I did that but it didn't work the first time around and it also brought the website down, it seems as though the records weren't fully propagated. I got in touch with Firebase and they said to try again, once they were fully propagated I got the green tick on Firebase but the next morning the website went down again.

What could be the cause of the website going down?

here is the CNAME & TXT records that brought the website down

Here is a screenshot of the records currently registered (minus the records above which had to be removed)

Here is a text file with the DNS records:

Solution 1:

My impression from the question is that for your domain example.com (whatever it is), what you refer to is the web site no longer working specifically means that you can no longer navigate to www.example.com in a browser as this name no longer has address records.

You have a wildcard *.example.com A, which covers any non-existent names, but as you describe in your question, you added records for the names www.example.com (TXT) as well as firebase1._domainkey.www.example.com (CNAME).
The side-effect here is that when you add these records, the name www.example.com now actually exists, hence the wildcard no longer applies here!

If you are going to add these other records while still having address records at www.example.com, you will need to add address records at www.example.com specifically (side by side with the TXT).