How do you separate crew when they're all together (1v3)?

I just played a game on Skeld where I was imposter and there were 3 crewmates left (1v3). I got a bit unlucky since the players I was trying to use for alibis were killed by the other imposter. Anyways, two of them had their suspicions on two of us since the two of them apparently stuck together all game. Well, after we booted the 5th, they just stuck together for the rest of the game. I had no clue how to separate them. When I or the dead imposter called sabotages, they still stuck together even for O2. We probably played for like 7mins like this. I eventually got super bored and frustrated from this playstyle so I just killed someone so they could vote me out. It kind of felt like a cheap way for them to win imo. What the hell was I supposed to do? Is there someone out there that masterfully beats such scenarios?

It was with some random people on a large discord server where I can find random groups of people to play with.

Edit: I realize the title is asking how to separate them, but the actual question is, "How do I separate them and win?"