The strike was just one of many things that killed the Expos. Not only were they severely low on cash (I think this was a problem even before the strike), they also had to contend with that ass-ugly stadium.
Trust me on this one. I've been there. Stade Olympique looks OK from the outside, but inside, it's a concrete shit hole. Players all hated it, too. And the premier of Quebec wouldn't authorize any public funding for a new ballpark - the Expos could certainly never have afforded it on their own - but here comes DC: Not only were they willing to build the Nats a new ballpark, they also had an OLD one they could use in the meantime.