I don’t think the main purpose of the Gish Gallop is to persuade anyone who’s in doubt. It’s a trick (one weird trick!) for winning debates. It depends on the fact that you can state a lousy argument more quickly than the other guy can refute it, so if you use all your time stating dozens of lousy arguments then your opponent won’t have time to deal with them all.
When used in that context it may be effective in persuading doubters—but it’s not that the Gish Gallop itself does that, but that seeing the other debater apparently overwhelmed by a torrent of arguments they can’t refute does it.
I don’t think the main purpose of the Gish Gallop is to persuade anyone who’s in doubt. It’s a trick (one weird trick!) for winning debates. It depends on the fact that you can state a lousy argument more quickly than the other guy can refute it, so if you use all your time stating dozens of lousy arguments then your opponent won’t have time to deal with them all.
When used in that context it may be effective in persuading doubters—but it’s not that the Gish Gallop itself does that, but that seeing the other debater apparently overwhelmed by a torrent of arguments they can’t refute does it.