Ludicrous to blame anyone for a defect in the bridge - these things happen.
What we can criticise is the (apparent) lack of planning for such an eventuality to occur. Given the importance of the route you'd have thought there would be a contingency plan in place that just needs dusted down when this happens.
Agreements with ferry operators, bespoke train and bus time tabling on trains, removal of some light controlled junctions etc. loads could be done automatically but doesn't seem to be