Matt knew that showing his power level in a public place like that would make the enemies he has in the dark more cautious, so it would be difficult to take them by surprise or off guard, as an assassin is always used to doing.
But this also means walking a different path than the one he once walked while on Earth. He doesn't want to go back to being that lone assassin he was in his past life. Where 90% of the time, his only company was Charlotte, which is why he has been changing and trying to leave the habits he had at that time.
This subject, although small, helps him in that aspect. That is why he was not afraid to show his power.
He doesn't care if the enemies they command from now on are more powerful; that will make him grow with greater speed, so it was the best thing to do at this point. He doesn't know exactly what Charlotte will use to try to get rid of humanity, but as her husband, he must help her somehow.
