So here's a crazy theory. We've met exactly one Silent in the whole game: Ciro. We also know that Ciro is involved in some elaborate cycle of amnesiac reincarnation, which s/he has repeated multiple times. So what if every Silent to pass through Underside was a different reincarnation of Ciro?
Probably the most interesting implication of that premise is that Al strongly implied he's seen multiple Silents come through the village, suggesting that either each cycle is quite short (i.e Ciro dies quickly) or Al has been down in Underside for a hella long time. Though we already knew that second one, not that we've tied an actual timeframe to anything.
This also ties into Ciro recognizing Al at the Greens.
Ciro can hardly recognize Al if s/he hadn't encountered him on previous cycles, and if Al was jive to the whole "cycle" thing then he would have known who Ciro was as soon as he fell down into Underside. Thus, Al thinks there's this whole class of adventurers he terms "Silents," when really he just keeps meeting Ciro over and over.
On top of that, it seems quite unlikely Al has ever left Underside before this cycle (we even got a whole cutscene out of it!) which would imply that Al's (and Cherish's) current Underside Exodus is a major departure from previous cycles. If that's true, then we should be really careful of Al and Cherish since it seems likely they'll be eliminated/reset at the first opportunity in order to "normalize" this aberrant cycle. Unless the reset of the cycle also gives Al partial amnesia.
Partial amnesia. Is there anything it
can't explain?