It would have been strange, yes quite strange indeed, for the authors to propose an amendment to give the government a power that was already mentioned in the constitution.

(https://autoadmit.com/thread.php?thread_id=5902859&forum_id=2#50130650)

that was particularly true in the Colonies because they all originated from express land grants from the Crown.

so it was a widely practiced concept and the 5th Am was an attempt to limit that power.

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The principle that the state necessarily owes compensation when it takes private property was not generally accepted in either colonial or revolutionary America. Uncompensated takings were frequent and found justification first in appeals to the crown and later in republicanism, the ideology of the Revolution. The post-independence movement for just compensation requirements at the state and national level was part of a broader ideological shift away from republicanism, which stressed the primacy of the common good, and toward liberalism. At the time the Bill of Rights was adopted, that shift had not been completed, but the trends of the revolutionary era received coherent expression in the thought of James Madison, the author of the Fifth Amendment's just compensation clause. Madison believed it necessary to erect strong safeguards for rights in general and for property rights in particular. His just compensation clause--although intended to have relatively narrow legal consequences--was such a safeguard. Its ratification represented the translation of liberal ideology into constitutional principle.

https://scholarship.law.georgetown.edu/facpub/1051/

(https://autoadmit.com/thread.php?thread_id=5902859&forum_id=2#50130717)