There are mainly three reasons to break a distribution strap:
1st bad assembly, excess voltage, when the engine works the belt is wearing much faster than normal due to the tensions that are generated in it.
2nd excess mileage in normal use without making the planned maintenance or intensive use of high motor regimes without shortening the maintenance periods or without incorporating a reinforced distribution strap.
3rd failure in the manufacture of the replacement, sometimes it happens, the bad is to demonstrate that it has started for this reason and not by the previous ones. (They grab a burning nail so as not to prove you right)
Other causes of breakdowns in relation to the distribution strap are:
carrying the strap too lazy, causes anomalous vibrations in the belt and although it does not look like it also stretches. In addition, carrying the strap too weaning can cause the distribution to skip one or more teeth when the engine revolutionizes, immediately destroying valves, guides, tachy and other organs.
That the service strap is broken (alternator, AA compressor, hydraulic pump of the assisted steering, water pump in some cases) and tied in the distribution strap, taking it out of its site and causing the immediate destruction of the engine.
All the best.