The story I've heard is that Congress was wary of the growing deficit and gave the president a choice of going forward with either TSSC or ISS. The political optics of a space station are much better than those of a super collider and there was still a desire to have aerospace projects for former Soviet scientists to be engaged in so they wouldn't end up working for a terror state. Had TSSC been picked over ISS, those Wall Street quants might have been kept busy underground in Texas but the folks who created the International Space Station would have been left to find their own opportunities, with unknown consequences.