"Why did teck make the deal in the first place?"

They were reluctant to incur the expense of the additional exploration.

Not sure exactly how the events were unfolding but Teck was either in the process or considering the massive Fording Coal acquisition and were deep into the Galore Creek project.

They thought, and rightly so, that by getting a competent explorer to do the legwork, they could have their cake and eat it too.

Don't think they had a clue how big the cake might be, as they were thinking that Galore was huge, and this thing is going to dwarf Galore....

They were also starting to get an inkling that Galore was going to be a questionable project based on material findings, and probably wanted to limit their exposure in the region.