Kerch is the waterway between the Black Sea and the “Sea of Azov” which is a rather large body of water (15k sq.mi.) Given that it is an international waterway, any bridge spanning it would have to clear large ships and thus be very expensive and long-time building.
Yeah it’s a really stupid idea, almost as stupid as Russia annexing Crimea in the first place.
A combo bridge and tunnel might work. The Bridge to Va Beach is 23 miles long. It’s only about 3 miles to replace the Kerch Straight Bridge.