In 478, Emperor Zeno attempted to orchestrate a battle between the two factions of Ostrogoths. He promised to provide the support of the Imperial army to Theodoric the Amal (soon to be the Great) against Theodoric Strabo.
He failed, and the rift within the Ostrogoths was temporarily healed.
What if Zeno had succeeded? Suppose the two Theodorics did not see their common interest lay in unity. The Gothic armies are devistated after fighting each other, and the Imperial army mops up the remnants.
What happens next?
There is now a power vacuum in Moesia and Pannonia. Who fills it? The Gepids perhaps? Do the Slavs come further west sooner?
What happens in Italy? Without the Ostrogoths, what does Zeno do about Odoacer?