Question: So even though Judas betrayed Jesus and caused him to be crucified, he still gets to be one of the foundations of the Bride of Christ?
There are several possible answers to this question. The first part is that Judas was not an apostle, after he betrayed Jesus and killed himself. He is called the son of perdition in John 17:12. Also, in Acts 1:15-20 the remaining apostles realized the need to find a replacement for Judas. So, Judas was not considered one of the 12.
The second part of the answer has to do with the fact that without Judas there was still 12. The first and easiest answer is that in Acts 1:21-26 they chose Matthias to replace Judas and thus there were 12 again.
But this is made a bit fuzzy by the fact that Paul was chosen by Christ to be an apostle later on. We see Paul talking about this in 1 Corinthians 15:9-11. Now there are 13 apostles.
The word apostle means “sent one.” There were several different kinds of apostles. We call them missionaries today. In the Bible, they can be sent by the church, as was Barnabas (Acts 14:14) or by Jesus himself (Acts 22:21). We usually capitalize the ‘A’ in Apostle when we mean Apostles of Jesus.
So, technically there were 13 Apostles.
The third option for what John was talking about in Revelation 21(which is where your question comes from), is that he is talking about the office of twelve apostles rather than the particular 12 guys. The Bible talks about the 12 tribes of Israel in the same way and the 12 Apostles corresponds, in the church age, to the 12 tribes of Israel. It is a title rather than a number. Because of the way John is talking in Revelation 21, I believe this third option is the right one for the context. The city is the church, made up of the members of the church, Christians, the whole context is symbolic and glorious. So, I think he’s talking here, about the office of 12 Apostles rather than the particular 13 members of the office.
I hope this helps.