Questions to ponder

Here are my thoughts on this:
John's baptism was "for the remission of sins" as he called out. It was symbolic in the sense that if you were a Jew indeed you had to offer a blood sacrifice to have your sin atoned for- according to the Law. However, the Jews' long disobedience and ultra waywardness had in essence placed them outside the baptism of Moses or the covenant. Their national washing took place in the Red Sea and their good behavior/obedience kept them in the covenant of promise. They disobeyed many times and God accepted them back after punishing them. However, the Jews had gone so far astray in the time of Christ that, in symbol, God placed a new circle outside the nation and, with God's authority, John came to baptize for the remission of sins. Whoever repented and washed, was brought into God's circle. Hence even Christ had to "fulfill all righteousness" by being baptized- not to have any sin forgiven- but to enter the circle that was no longer around the Jews.

"Did it forgive the participants of their sins?" Yes, I believe God gave John the authority that whoever submitted or humbled himself to baptism was washed of his past sins but that did not stop the person from having to offer the blood sacrifice. It just brought him in the circle of God's presence to be able to offer and the offering to be accepted. I believe this will answer the next question as well. The sacrifices was the manner that the Jews got their sins forgiven- but as Paul states- the blood of bulls and goats could not take away sins- so they had to have faith that God would remove their sins somehow, not through the blood of the animal but by God's grace.

John's baptism was unique for a set period. It was temporary and could only be so. It was transitional. Those that were baptized with John's baptism only had an idea of the fact that they were in God's circle now but they were no better than any other Jew from their past 4,000 years- in need of true redemption from Sin- their nature. These believed in a Messiah but it did not connect the Messiah to a specific name before the rite of baptism and could not, until the crucifixion proved that Jesus' name could and would be the one. Hence re-immersion was necessary except for the 12 apostles that were cleansed by the Word's washing as he stated in John's gospel. All others had to connect the name of Jesus as the true sacrifice who's blood indeed took away their sins. Now with the new-found faith in the actual person and not just a Messiah, with their faith in accepting Him as the only name that can save, and with their faith in accepting that the animal sacrifices had no efficacy- these allowed a person to rejoice and re-submit to the baptism of Jesus.