Taken Trumps comment in entirety I think he was saying that compared to the other violent protests and how those people walked basically he believes the Jan 6 people were unjustly treated...that it was unfair to treat them this way while the other ones never paid a price.
So I don’t think he means to pardon everyone, rather he would be fair. Because not everyone who was there were guiltless.
That’s a pretty subtle point to be driving for someone who sent 700 followers to the bowels of prison just for demonstrating and expressing their political opinions and remaining relatively silent about it for more than a year.