There are metal bridges over 100 years old still in service today, including a few you've heard of. Do you know this specific bridge was replaced for this specific reason, or are you just making stuff up?
The question was why this specific steel bridge was replaced. Not "what are possible reasons someone could replace steel bridges?" and it's absolutely not "basic materials engineering" that every bridge needs replacing after a fixed amount of time due to corrosion.
So again, do you know this specific bridge was replaced for this specific reason, or are you just making stuff up? Because bumping in on a specific question with a generic answer without any knowledge if that applies to this specific case is making stuff up.
The hostile tone is because you're talking complete nonsense with great arrogance.
This is basic materials engineering.