I think there’s a difference between a muddy/sandy chain and a poorly lubricated/waxed chain. Waxed/lubricated chains address the friction within the rollers and links. If there is mud/sand on the cassette or anywhere else in the drivetrain other than within the rollers and links, then it’s essentially beyond the power of the wax/lube to address. Not sure if that makes sense the way I’m describing it, but I’m just trying to avoid misattributing noisy chains to ineffectively waxed/lubed chains. I’m not surprised that a quick re-lube quieted the chain down, you’re essentially washing it. If you have waxed your chain, I suspect that quick water spray would be best - newer lubes will frequently have solvents in addition to lubes that serve to clean the chain while lubricating at the same time.
Just my $0.02