This is the IDers having to pivot yet again…
It used to be, “explain the flagella”
So scientists looked at each stage of flagella development and lo, and behold, they found each step and that each step encountered a development having nothing to do with a flagella but each step conferring an advantage in cellular pumping or cellular exchange. The final step was adding a flagella that gave motility…another advantage. The process never had a flagella as it’s goal. It’s just where it ended up. These little surprises happen all the time.
Now, the pivot…well, what about multiple flagella that run in sync? Why not see if you can figure out how a system that developed one flagella that allowed mobility might just develop multiple flagella to increase that motility! I’m retired. I’m done with working but you may have time to discover the answer!