If it is in fact snails, then regular insect poisons don't work. There are several snail threads on this board. But if I were you, would scout around the garden area, looking under crawl spaces of things, looking for slugs. I just started hand gathering my slugs from their hiding places. Will limit activity to that and perhaps a couple of beer traps for now. I collected over 100 slugs yesterday. There are various snail baits but don't know compatible they are with a garden area. Bell pepper will do just great in 3 gallon containers, that would allow you to move them to different locations to perhaps avoid the problem. But at this point, your issue could be most anything from rabbit, to deer, to whatever. I don't know what critters tend to decimate a pepper plant, but do know that they can be a target of snails, so tossed that out just as a possibility.
Try to get a handle on what is actually causing the damage before getting to involved into what to do about it. In the mean time, I would consider buying some replacements and at least temporarily letting them grow in containers that could be moved around. Bell peppers will grow very quickly in one gallon nursery pots. If you chose to leave them in containers, then as mentioned above, you will want to step them up to a true three gallon size.
Eclectic gardening style, drawing from 45 years of interest and experience. Mostly plant in raised beds and containers primarily using intensive gardening techniques.