I think the idea of more opportunities to cross is good but the pricetag is absurd still. After all, they are terraforming a hillside. I think it is a little misplaced though. We assume animals need this to cross but it seems they can take a regular old bridge just fine. You can probably build a cheap "animal only" overpass, e.g. maybe a light load mesh metal or plank bridge or somesuch, for a fraction the cost and offer many fold more crossing opportunities across more of the freeway vs just one big budget spectacle. I'm sure the contractor was connected in some way. A sort of storm drain like underpass design would probably also be cheap if done during routine freeway work.
Instead of guessing you could look into the research literature on animal road crossings. Its a surprisingly large area of study because it is hard to get animals to use these constructions. Maybe they did a bad and expensive job, but you have nothing to base that on at all.
I base it on the mountain lions in question already urbanized enough to walk on sidewalks in los angeles. I mean there were people seriously claiming the griffith park mountain lion was somehow isolated to griffith park, and yet it was showing up on people's ring cameras miles away from the park. I think a lot of people assume that animals are only found in "nature" and don't know what to do in an unnatural setting. They can figure it out. Look at your housecat figuring out your entire home, and realize this is basically a smaller brained mountain lion.
Do you know how much accidents cost? $100M is nothing in comparison over the long term. Plus this was a 10 lane overpass and a unique build during a high inflation period. That is not simple terraforming amigo.