Admittedly this passage is very difficult, but there are some parallels in the gospels that we must compare with similar passages in the Hebrew Bible. In other words, our fundamental hermeneutic is to interpret Scripture with Scripture.
First, when we find Jesus on the Mount of Olives, he is in the company of a crowd of people according to the gospel of Matthew. That is, all three synoptic gospel accounts indicate that Jesus migrated to the Mount of Olives from Jerusalem, but Matthew is the only gospel to emphasize that there was a "crowd" with him on the Mount of Olives (Matthew 21:8).
When King David was on the Mount of Olives (when he was in exile because of rebellious Absalom), there were two donkeys that arrived on the Mount of Olives that were carrying bread, raisins, fruit and wine destined for Jerusalem (2 Sam 16:1-2). This passage indicates that these donkeys were intended to be mounted by the King (Absalom) for whom the provisions and foodstuffs on the donkeys were refreshment for his companions. There is no mention of whether or not David confiscated the load of goods (or the donkeys), but the amount of foodstuffs is almost exactly parallel to what Abigail provided to David's 600 men (1 Sam 25:13), when she loaded donkeys with the same foodstuffs for David and his companions (1 Sam 25:18).
In other words, Jesus mounted the single colt to enter the East Gate of Jerusalem as the deliverer of Israel (the Messiah) in parallel to both Zechariah 9:9 (complete fulfillment) and Ezekiel 43:1-4 (partial fulfillment). But this story starts with two animals and ends with one. That is, the colt and her mother were already loaded with foodstuffs (when they were retrieved by the two disciples) so that (a) Jesus could feed and refresh the crowd that was with him on the Mount of Olives; and (b) to take and ride the single colt into Jerusalem. To put it another way, if Jesus is on the Mount of Olives as the rejected king (like David), then the two asses (donkey and colt) carried the foodstuffs and refreshment for the crowd of several hundred people who were with Jesus on the Mount of Olives in the very same form and fashion as had occurred when King David and his men were on the Mount of Olives.
Finally, both Mark and Luke focus on the triumphal entry into Jerusalem (and thus the emphasis on one animal that was mounted by Jesus), but Matthew is the only gospel that expands the sight picture of the triumphal entry, and includes an emphasis and therefore mentions the "crowd" with Jesus on the Mount of Olives. (The other gospels simply mention the unidentified "they" who were with Jesus, and Luke uses the word "crowd" only after Jesus had begun to leave the Mount of Olives.) My own personal view is that the two animals (donkey and colt) were retrieved by the two disciples fully provisioned with foodstuffs and refreshment for a time of preparatory celebration, but only one of them (the colt) was mounted by Jesus into Jerusalem. The key parallel in the Hebrew Bible again is therefore 2 Sam 16:1-2.
There are therefore no contradictions in the gospel accounts, but simply an amplified view from the perspective of Matthew, who captures the very details of prophecy and the very nuance of David the rejected king on the Mount of Olives. Such an emphasis is not a surprise, since Matthew is the "regal" gospel and therefore has placed an emphasis on Jesus as the Son of David.