Understanding Maimonides’ words in the Pihamash about the Sanhedrin

Maimonides in Sanhedrin Laws 57:43 writes, “And you already know that the witnesses are the ones who kill with their hands whatever death there may be, since the same thing is clear to them since they saw it with their senses, and with us it is nothing but a story, since we have no knowledge except what we heard from them, and therefore God commanded that the witnesses themselves be in charge of the matter. And this is a wonderful thing.” I did not understand why Maimonides emphasizes here that it is wonderful, something he does not usually do. If the rabbi has an idea of ​​how to understand things, I would be happy to know.
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