Are they crazy?
The Turks had at least one rail tunnel under the strait, I believe, and over the past ten-fifteen years have been digging a newer system that will take much more traffic volume. In the process of this, they’ve turned up ancient ships, wharves, etc, and other ancient sites that had to be rescue-dug.
The bridging of the straits in ancient times was accomplished at least twice by the Persians, hmm, maybe three times, using pontoon bridges. They built a bridge for the Greek war, the one that included the militarily insignificant Thermopylae but was answered decisively at Salamis. The Persians also bridged it for their campaign into Scythia, which turned out to be a huge waste of their time, because the Scythians lived in the saddle, and would just bug out when they saw the cloud of dust. As the winter started to close in, the Persians marched out as fast as their feet would carry them. Odd that neither Napoleon nor the WWI and WWII Germans didn’t learn from this.