Candles can't dehumidify a room because they burn hydrocarbons and produce moisture when you light them. If a candle were to reduce mold, it would be because it burnt something toxic to the mold.

And radiators dont cause mold? The heat and moisture may give the mold perfect growing conditions, but the moisture is what you want to get rid of. Use vents, fans, open a window, air out the house, use a dehumidifier.

Burning a candle to prevent mold is a shitty tip.