The SWR meter indicates the value from the meter to whatever is after it.
If you insert a device that has a high SWR (because it becomes defective or
for some other reason ) between the transmitter and SWR meter ( say a switch
or filter), the meter can show a low value if the antenna is ok, but the
transmitter will see a high SWR and may burn out the finals.

He did not say he inserted anything, just that moisture at the end of his
transmission line caused a fault. If this was the case, an SWR bridge at the
output of his Power Amps should have alerted him to a problem that would
potentially destroyed them.
If you want to use an SWR bridge as a protective device, or indicator, it
must be placed in the proper position in the antenna system. Modern
transceivers have circuits that detect mismatches and reduce power to minimize
failed output devices.


73 Gary N4AST