Yes. Bruce that is a common enough misconception but I hope I can provide a bit if insight if you want. The Dark Powers do not surrogate as the source of power to clergy. Those gods do exist, its not a question, and a good deal of characters from other worlds would not question their existence or lose faith just because they are inside the Demiplane of Dread. The relationship between mortal godservant and deity in far off outer planes would experience such a deviation in feel though that it could bring about a crisis of faith, as opposed to a loss of faith. The nuance being that they would question whether or not their actions are befitting the favor of their god without ever actually knowing for certain or not. They have to trust their self to uphold the missions of their church without divine influence and often without the support of their fellow mortal clergy's affirmation. Its like the theme of Ravenloft in general at play again, the cleric is experiencing a crucible.
DPs step in when a deity has stopped giving favor due to severe deviation of faith. In other settings the deity's disfavor would be well known more or less because prayers are no longer answered with spells granted. And to regain spells and powers a supplication and atonement would be minimally required. Or even atoning quests would be required to regain sponsorship of their patron deity involving long and drawn out tests of loyalty and faith. In Ravenloft the cleric gets no such affirmation of loss of favor, nor is there any spelled out path to redemption, and they would not know they have lost favor because the DPs have made sure the spells are still granted in a deity's absence if the cleric still prays to a god that has abandoned them. That's the time a surrogate relationship occurs, its not a feature of the setting that the gods don't have reach into the demiplane. They are gods after all, they just have limited ability to affect the world, limited more or less to the affairs of their mortal clergy with only their dogma and not divine intervention to guide their hand. In some ways I've enjoyed roleplaying clerics in this scenario even better than in their native environment. There is something unique and challenging about being the lone or near lone agent of a church with only the upbringing and dogmatic beliefs to guide the character.
Also, Gods that actually do not exist at all and never have might have the DPs acting Divine Sponsor, but thats rare and specific.
