John tells us Jesus fed 5,000 just before Passover. Matthew tells us Jesus had just heard about John's beheading earlier in that day. Mark tells us that Herod Antipas made a reference to Purim when his stepdaughter tricked him. This really can't be a coincidence, because Purim always falls about a month before Passover. Therefore, if all three writers are to be trusted on these points, the reconstructed event sequence should absolutely be taken as historical.
[Dating these events is another matter, but in 31 AD, while Sejanus was still alive, the Feast of Purim was Saturday night, February 24th, and the Passover night was Tuesday, March 26th.]
With this added perspective, we should approximate that Antipas' birthday celebration was held around or shortly after Purim. Most likely, Antipas invited the same guests from the earlier Feast of Purim, guests who would undoubtedly have expected a recitation of the Esther story by a professional or court speaker, in keeping with the Tetrarch's high status. In any such context, Antipas' birthday promise, "Whatever you ask... up to half my kingdom" can be recognized as an artful nod to the recent event's entertainment, with a clever wink to his guests.
Far more importantly, this all goes to show that the sequence of events in all four Gospels, at least at this stage of their narratives, was very much non-arbitrary. Three different Gospels offer three separate details that allign perfectly into one historical sequence. Luke's Gospel confirms the sequence and adds that the 5,000 were fed at Bethsaida. Point: all four writers had a stronger historical sense for relating events than they are sometimes given credit for.
John's beheading is clearly the most significant event during Jesus' ministry, so it makes sense that each writers' event sequence would sharpen in focus around that point in each narrative. The same holds true for the Lord's Passion week. So while there are many other challenges for Event Sequencing the content of the Gospels, this particular chain of events is encouraging because it shows the need for (and the validity of) using all four Gospels in reconstruction.
Sequence is the first step in chronology, providing perspective to history.
Event sequencing in the Gospels is vital to any historical view of Jesus' ministry years.