If you look at the break right above the spoke in the 1st picture, you will see a spot that looks discolored, this could be an indication of a pre-existing crack that expanded.
Look at my previous post about metal crack analysis.
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Il faut de l'audace, encore de l'audace, toujours de l'audace
1980 3Rensho-- 1975 Raleigh Sprite 3spd
1990s Raleigh M20 MTB--2007 Windsor Hour (track)
1988 Ducati 750 F1