Meanwhile, the black knight has long term prospects to infiltrate white’s position.
General speaking, knights fare better in closed positions and bishops fare better in open positions.
Great question @deathb3rry Questions like these show you are trying to learn and I'd like to see more forum threads like this around
Yes, there were other moves than en passant, but that is a key candidate move to calculate because it fights against the idea of a closed position. However, other moves such as O-O-O or a4 were also good according to the engine.
The reason that the Knight is better if e5 is played is a complicated one and such a subtle nuance that it would be difficult for even intermediate level players (not just beginners) to convert. The short answer is that generally speaking Knights are better in closed positions and Bishops are better in open positions.
IM Jeremy Silman is famous for his "imbalances" taught in the book, How to Reassess Your Chess 4th Edition (the first 3 editions were built up on each other, but the 4th edition was completely redone with new examples and more concepts and is the famous one). There was also an article on chess.com by Silman called "The Eternal Knight Battle" but I can't find it anymore. It discussed the Bishop vs Knight imbalance well. Maybe I can find it because it was a good read.
https://www.youtube.com/watch?v=AabQc8HJkJM&t=360s&ab_channel=SammyChess
As per the narration, "he plays e5 creating a closed position where his knight can dominate the white bishop." I understand the closed position created but how does black knight gain the advantage? If white did not en passant, was there a better move he could do and how would black respond?