It is uncertain whether these resurrected saints died again or were caught up to God. If they were resurrected at Christ's death, then they would have had to die again, just as Lazarus or Jairus' daughter or the widow's son at Nain or anyone else that Jesus raised from the dead during His ministry. This is because Jesus was, "the firstfruits of them that slept" (Acts 26:23; 1 Corinthians 15:20). Jesus was not the first person physically raised from the dead, but He was the first person begotten from the dead to never die again.
If these people were not actually resurrected until after Jesus' resurrection, when Matthew states they came out of their graves, then they could have been resurrected with their glorified bodies to never die again.
At any rate, these saints went into Jerusalem after Jesus was resurrected and they appeared to many people. We can only guess what effect this must have had on the people.
The resurrection of Jesus puts Christianity in a class all by itself. Many people have come and gone professing some revelation from God or new way of approaching God. But only Jesus has conquered death. This makes Him unique and elevates Him above the level of any other man who has ever walked on the earth. The resurrection of Jesus is the ultimate proof of the accuracy of His doctrine.