He did not roll that nat 20 heck he probably got a nat 1 with negative modifiers
If we're being honest this is probably multiple checks he failed with possibly 1 Success:
(Optional) Performance: Acting as Wolf-Senpai's tutor and as a somewhat different person to his usual self. (technically not deception he is quite literally performing) He rolled a 3 Wolf-Senpai rolled a 1 on insight.
Stealth: Trying not to get noticed by his peers. Fails immediately.
Deception: Failure of trying to convince his peers he's not himself. Rolled a 2. Only gets bailed out by Wolf-Senpai. Who let's just say automatically failed insight again.
Stealth x2: Rolls a 1 and encounters his family.
Saying this right now they both have wisdom of like 7, one for not thinking this plan through, the other for not seeing anything. Also there are a lot of more checks I could probably find.
Yes I love Dungeons and Dragons how could you tell?