It's a party
It was not the fact that Larry was in the Golden Core realm that surprised Lex, although that in itself was an achievement beyond unbelievable. After all, Lex himself had a cheat-like system and access to multiple worlds and realms and beings of unimaginable power, yet he himself was only now about to enter that realm. Yet Larry, who did not have a system and was trapped on earth, except when he was at the Inn, had somehow surpassed his speed. In fact, not only was his speed in reaching the realm remarkable, based on the fight, Lex could tell that his cultivation was not shallow either. He possessed strength that could not be achieved by someone who had only rushed his way through cultivation using resources.