Because John baptized with water and Jesus baptizes with the Holy Ghost...
Some people received the Holy Ghost without water baptism by repenting (believing on Jesus)...And of course some were baptized with water and did not receive the Holy Ghost...Showing that water has nothing to do with receiving the Holy Ghost...
You’ve got a different version than the Bible has in Acts 8 and 19. That’s how you end up with more baptisms than Paul says there are.