The Keystone XL permit was originally denied, then (illegally) approved by Executive Order. The nature of Executive Orders is that they can be, and frequently are, tossed out by the next guy in office. This isn't a big secret, so I don't have a ton of sympathy for anyone who "spent billions laying pipes" under a permit granted by EO. If they wanted a lower risk of losing everything, they should've waited for the standard permit process, instead of gambling on the EO and that Trump would win another term.
It was political from end to end, and was never denied on fundamental grounds, but instead has been governed by protectionism. What made it particularly farcical is that at the same time Obama was pontificating about the horror's of Alberta's oil and turning an environmental new leaf, US shale oil exploration (just as bad in every dimension) was growing at a staggering pace, and is now multiples the output of Alberta's oils ands.
The quicker we transition to renewables the better, but the farce of Keystone was always just politics.
