Econometrics design comparing time periods

Dear all,

For my thesis I want to compare the effect of cultural fit on cumulative abnormal returns (CAR) in mergers and acquisitions. Theory has shown that less cultural fit negatively impacts merger performance. During covid, with remote working, it is more difficult for companies to softly check whether they match culturally and to integrate companies.
I would like to the best research design to do so.
I thought of comparing merger performance from March 2020 to August 2021
merger performance of September 2018 to December 2019.

My hypothesis is that the cultural fit variable of March 2020 to August 2021 more negatively impacts merger performance than before.

Is just comparing these periods and making both periods relatively similar (selecting firms that are similar etc.) an okay research design? Or should I have different approach? Anyone has suggestions for a better empirical design?

My main question is: How can I analyse the effect of covid pandemic post-merger integration and hence post-merger performance?