Who benefits from the notion that the healing of the paralytic and the teaching on the mountain were the same event?
Just because both involved Jesus and a crowd does not mean they are interchangeable; this does not capture the motivations.
The healing of the paralytic was an immediate display of power to establish authority, a strong signal to skeptics.
The teaching, on the other hand, was a long-term investment in training the disciples, requiring a deeper commitment.
For example, for a leader seeking to rally initial popular support, a public miracle is more effective than hours of complex speeches.