Easily topple a kingdom while difficult to keep it

[NewHope]

For Microsoft, it is easy to topple the old kingdom of software, but not easy to keep the power of new kingdom in its hand.

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I'd like to know if there is an idiom in English to express the meaning of the title.

[Tdol]

There idea's plain, but I can't think of one.

[twostep]

There idea's plain, but I can't think of one.

It is just to early in the day for you to function - after all you are a night owl. :wink:

It is easy to take something from someone else but difficult to hang on to it.
You can take over a company by various means. Will you be able to keep it and have it prosper?
You can get the perfect job but will you be successful at it?