In Mark 2:1-5, verse 1 says, "And again he entered into Capernaum."

The word 'again' indicates that Jesus must have been there before.

Mark 1 mentions the first time He went to Capernaum that many sick were healed, many devils were cast out and that Jesus performed miracles all over the city.

So when Jesus returned, word got around and soon the house where He stayed was packed .