“They told them
What Jesus had said.
They allowed them
To take it.”
οἱ δὲ εἶπαν αὐτοῖς καθὼς εἶπεν ὁ Ἰησοῦς· καὶ ἀφῆκαν αὐτούς.
This is similar to Luke, chapter 19:34. Mark said that the response of these 2 disciples was what they had been prepared to say. They told them (οἱ δὲ εἶπαν αὐτοῖς) what Jesus had told them to say (καθὼς εἶπεν ὁ Ἰησοῦς). Thus, these people in this town allowed these unnamed disciples to take the colt with them (καὶ ἀφῆκαν αὐτούς). Mission accomplished!