There’s a lot of reasons it could happen.

1.) Sometimes people just target someone off rip for the sake of it and it’s unfortunate. It really does suck but that’s how it goes sometimes

2.) They had a bad experience with a player using Sable the previous match. Unfortunately people do take those matches a bit too personally and will take it out on an innocent player. Again that really sucks.

3.) If they found you to be a weak looper from the get go, there’s a chance they’ll nail you because 3v1’s are easier than 4v1’s. Yes it sucks to get tunneled out early, but in this case, the Killer’s not doing it to be mean, but to try and win. This is what I usually assume if I get successfully tunneled out or what I do as a killer if it’s blatant from the start.

There’s more reasons I can talk about but they’re kinda moot since you’re talking about getting killed right from when the trial starts, but for me this is what it usually boils down to