meaning of "staple offering"

[Learning_English]

Cricket's pinnacle event returned home to England for a fourth time after a gap of 16 years. The evolution by now had subsided as the One-Day International format took charge as a staple offering of the gentleman's game.

Please explain the highlighted sentence.
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[Learning_English]

To book a berth meant that they were certain they would have a proper place to sleep on the ship. Those who had not booked berths had no such certainty. They might not have any place to sleep, or perhaps they slept on in the cargo hold, or down by the keel or on the deck. They hoped they would get a decent place to sleep, but it wasn't certain. Anything that isn't certain has an element of chance in it. To board a ship without knowing that you would have a place to sleep on it was to "take a chance" that they would not get one.

Please explain the bold group of words.
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Please let me know if I have made any mistakes in any of my sentences.