Because there were no "Engineering Studies" on it and the State can't have anything that doesn't meet their own ridiculous standards.
That's OK though JP, they replaced it with a metal Howe Truss bridge that looks close to the original wood bridge that burned... Close is the operative word here.
It's the same reason that they took the pin truss bridge out of service to put "I" beams underneath it. That bridge held up Standard Gauge UP 2-8-2's but it wasn't good enough to hold up a 3' gauge diesel.
That's what you get when you have too much lottery money and no brains behind the way you spend it.
Rick