It's pretty clear.
CoO measure the rival's strength like we saw with Rayleigh and Coby and Sanji stated quite clearly that P1 was an easy opponent, so he took advantage of it to test the suit since he could destroy him anytime he wanted.
Drake was sent after him after that. If P1 was still avalaible for combat, he would go himself since Sanji "supposedly" ran from him.
And now it was proved again that Sanji is a whole lvl above Tobi Roppo with Black Maria being the 2º strongest without being able to deal any relevant damage to Sanji despite his CoA went "limp" while a normal CoA would injure BM without even he exerting extra force.
Only in Zorotards heads Sanji didn't destroy this fodder, which does not matter at all since manga > their headcanon.