i think that dumbledore did trust snape cause he would have not let him stay in hogwarts near harry potter if he didn't and also voldermort trusted snape to spy on dumbledore and hogwarts people and i think that the malfoys trusted snape also beacuse draco's mother made snape do a vow if she didn't trust him then she wouldn't have went to him only harry potter and bellatrix don't trust snape for sure