humans are slightly easier to deal with as we follow signs and are smart enough to not try to outrun a train. (well most of us are).
Deer get hit by vehicles on the highways all the time, so are you going to stop driving?
They certainly could do something, but it all comes at a cost and just wait for the complaining when costs of stuff go up because they somehow put animal control on thousands of miles of rail track. Its just not practical.
The train didn’t just hit a deer. It hit over a hundred antelope so far this year. Likely all within a 50 mile stretch of track.