Lately, there’s been a lot of talk about on-chain large transfers and hot/cold wallet movements at exchanges, with people saying "smart money is coming/going"...

The more I see, the more I want to ask: when this money crosses chains, who do we really trust?

Honestly, a cross-chain message (whether called IBC or a bridge) usually involves trusting several layers:
The source chain itself—don’t roll back or have strange finality;
The intermediary relayer or message sender—don’t cheat or get stuck;
The verification system on the other chain (light client, validator set, threshold signatures, multi-sig committee...)—must not be compromised;
And finally, the deployed contract/module—must not be written with vulnerabilities.
IBC’s approach is more like “I run a verifier on the other chain that can verify your blocks,” while bridges are often more like “I trust a group of people or a set of signatures to say that something happened on your side.”
The former is more complicated but trust is narrower; the latter is easier but, with more “people,” I start to feel a bit uneasy.

My mom asked me a couple of days ago: isn’t cross-chain just transferring money from A to B?
I said it’s pretty much that, but actually, it’s about transferring a “proof”—the key is who has the authority to say what happened...
Anyway, I’m not in a rush to interpret hot wallet movements right now; I want to think first about the bridge they’re using and whether the trust components are too long.