" none of them were "independent witnesses". And none were eyewitnesses, of course, as the events and persons, including the "Jesus" Figure, are all Fictional in the Gospel of Mark, a Work of Fiction. A Work that is just a Fictional as the one about Apollonius of Tyana.
Thanks for posting PP, it is interesting to see the process at work of adding to the the first Story, and deliberately changing it.
This is a process that started as soon as Genesis was written, and carries on all the way through to "Revelation".
A constant process of Editing, Redacting , inserting many Interpolations etc.