But if you give them hints and clues it implies there's a choice.
I mean suppose the evil guy I mentioned who just happens to be the only way to accomplish something (find a villain who the PCs couldn't locate, break into a tower that is sealed) is created with copious hints to his evilness. Coal black eyes. Dresses all in black. You see smoke creeping out of his robes occasionally. He sometimes starts chuckling malevolently.
If he's the only way to accomplish what the PCs want to accomplish, they still have to follow him around.
It's only if he offers the PCs an EASY way to find the villain but the PCs know that there's hard ways that might involve expenditure of time, money, influence, etc. that there's a choice. The PCs can choose to follow the possible villain, the easy route, or rely on their own devices.
Even there, it's not a compelling hook unless most of the time the NPC doesn't betray them. Otherwise it's like "well we could take the obvious trap option here." And if you do that the few times the NPC DOES betray them can end up feeling like the DM is betraying them (because in the past, X worked, and now X doesn't!).
At the end of the day, I like betrayal to come about because of player choices. Maybe they had a loyal ally who wished to gather knowledge for the advancement of civilization, and the PCs ended up burning down a library full of irreplaceable texts. You can play up his shock and horror at the event, then later when the PCs find a knife in their back because they trusted him to still be loyal, there's a sense of connection. They realize it's a consequence of what they themselves chose to do. That takes away the feeling the DM betrayed them (if done properly) and actually reinforces their trust in the DM - the NPC had logical motivations and they themselves chose not to respect those.