How was the research eye-opening? There are many partisan think thanks that give their opinion. This pipeline would've added 1M jobs to the US economy, obviously not directly employed (which is the media skimming over a LOT of details and economics) by the company but it is an effect it has.
Even today, there are 11,000 people working on the project and this project has been going on for years now and will for many more. That isn't a drop in the bucket.
Do research, but also understand what the research means and all its biases. Obviously everything has a side effect, both positive and negative, but these engineers involved have built pipelines across the world without major environmental disasters and this particular line is so over-engineered it's unlikely to fail even if it was totally neglected for a decade.
Even if you ignore everything, just think logically. This guy has been President for what, 24h and he suddenly has all the information to make a balanced decision? Even just the legal implications (Presidents, unlike what the media tells you don't have unlimited power) would've taken weeks if not months to research, the President does not have unilateral power to just cancel a permit that has been provided.