Sometimes when you see a theme, it starts to appear everywhere. That is what is happening with the ancient Greek truism that people in a crowd are more vulnerable to persuasion in a way that the individual is not. Two more instances:
The Athenian ambassadors spoke as follows: “Since the speeches are not going to happen before the majority, there is no way for us to deceive the listeners and seduce the masses once and for all with uninterrupted speech safe from cross-examination (for we know that this is the reason we have been led before the few)…
οἱ δὲ τῶν Ἀθηναίων πρέσβεις ἔλεγον τοιάδε. ἐπειδὴ οὐ πρὸς τὸ πλῆθος οἱ λόγοι γίγνονται, ὅπως δὴ μὴ ξυνεχεῖ ῥήσει οἱ πολλοὶ ἐπαγωγὰ καὶ ἀνέλεγκτα ἐσάπαξ ἀκούσαντες ἡμῶν ἀπατηθῶσιν (γιγνώσκομεν γὰρ ὅτι τοῦτο φρονεῖ ἡμῶν ἡ ἐς τοὺς ὀλίγους ἀγωγῆ)…
Thucydides 5.85, in the opening gambit of the Melian Dialogue.
And the common people marveled [at the arrival of Alcibiades and Chalcideus] and were concerned. The conspirators had arranged that the council happened to be in session, and Chalcideus and Acibiades gave speeches, saying that many more ships were on their way and concealed the naval blockade around Speiraium. So first Chios and afterward Erythrae revolted from Athens.
καὶ οἱ μὲν πολλοὶ ἐν θαύματι ἦσαν καὶ ἐκπλήξει: τοῖς δ᾽ ὀλίγοις παρεσκεύαστο ὥστε βουλήν [τε] τυχεῖν ξυλλεγομένην, καὶ γενομένων λόγων ἀπό τε τοῦ Χαλκιδέως καὶ Ἀλκιβιάδου ὡς ἄλλαι [τε] νῆες πολλαὶ προσπλέουσι καὶ τὰ περὶ τῆς πολιορκίας τῶν ἐν τῷ Σπειραίῳ νεῶν οὐ δηλωσάντων, ἀφίστανται Χῖοι καὶ αὖθις Ἐρυθραῖοι Ἀθηναίων.
Thucydides, 8.14.2, at the outset of the Ionian War.