Bosphorus is not suitable for heavy cargo shipment. Many crashes happened till today and there happens a lot of near-crashes every year. There are buildings everywhere in the shore of Bosphorus and people live there. Even if luckily no casualties happens, there are historical buildings including Dolmabahce Palace. These buildings are too worthy and most of them are unreplaceable. You can't just wait and watch while a big crash may happen anytime.
There are few more reasons that makes the Bosphorus not fit for shipping. Mostly because of the underwater structure of Bosphorus, streams and it's curvy nature. These causes a huge lost of money annually.
I'm not a master in treaties either but if I'm not wrong, we can not control civil shipping in bosphorus. We only can stop military ships and only in under some conditions. Idk much but what I know is treaties about Bosphorus has a lot of writing in it. No doubt these are pissing our government. Canal will let us stop shipping in Bosphorus because we will tell the world it is risky to do shipping there. And we will force them to go from a route which we have full control on.
About investment to Istanbul or Anatolia, I'm living in Samsun since I was 1 and I've seen most of the cities in Turkiye. I won't be able to join your thoughts. We have a whole area in Samsun that only factories and such industrial buildings are there. You all know Canik, which is a sub-company of SYS (Samsun Yurt Savunma), has factories in Samsun and has a great piece in exports of Samsun. Chery is also getting ready to establish a factory in Samsun (in new industrial complex).
I've spent a quite time in Bursa, which is home to a lot of factories including a lot of car manufacturers.
Similar amounts of factories in a lot of cities such as Konya, Gaziantep, Yalova, Sakarya, Kocaeli and so on..
These cities get a remarkable amount of investment. I'll give an example over Samsun again, the new industrial complex I just mentioned is built to be home to factories and industrial buildings. Hundreds of companies and manufacturers are going to be there and this will exponentially increase production in Samsun. BYD is investing 1 billion dollars to Mersin now. There are factories of Turkish defence companies all around Turkiye, TAI is heavily investing in Kahramanmaraş since the earthquake.
Long story short, there are investments aiming Anatolia, which I witnessed some with my own eyes. And there is a NEED to build a canal in Istanbul, otherwise possible crashes will create a small earthquake effect.
Most of you are living abroad. This makes you miss a lot of news and you don't see Turkiye with your own eyes as much as I do. So please pay attention to what I said.