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Raspberry Pi becomes a public company
(www.theregister.com)
This is a most excellent place for technology news and articles.
In general the reasons could be, an opportunity to raise capital meaning they can ramp up production or produce a better product, and/or the current owners want to cash out.
Most of the time is for the owner to cash out. Either now, or in a short time when the ramp up is done, for more money.