Although the customer set 1 million to [Maximum number of rows to export to Excel] at Client performance options page,

exporting data to excel fails before 1 million rows on many forms due to FormDataRecordTempTableStore table limitation. 

Customers request to fix this issue to be able to export 1 million rows to Excel from any forms.

(Related article)

https://experience.dynamics.com/ideas/idea/?ideaid=d77754a4-605e-e811-bd6d-0003ff68bdcb

https://experience.dynamics.com/ideas/idea/?ideaid=6f4d77d0-57f5-e711-80c0-00155d7cd0b4

Export up to 1 million rows to Excel

https://docs.microsoft.com/en-us/business-applications-release-notes/october18/dynamics365-finance-operations/export-more-rows