Maybe you incidentally selected all sheets.

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Select sheets in a workbook

If you select more than one sheet, Microsoft Excel repeats the changes
you make to the active sheet on all other selected sheets. These
changes may replace data on other sheets.

To select Do this

A single sheet Click the sheet tab.


Two or more adjacent sheets Click the tab for the first sheet, and then
hold down SHIFT and click the tab for the last sheet.

Two or more nonadjacent sheets Click the tab for the first sheet, and
then hold down CTRL and click the tabs for the other sheets.

All sheets in a workbook Right-click a sheet tab, and then click Select
All Sheets on the shortcut menu.