Does sslstrip have to do something with Bettercap’s certificate?

I am trying to perform a MITM attack using bettercap against a website that doesn’t have the HSTS security policy implemented at all.

When I try the following command: bettercap -T AddressIpoftheTarget -X --proxy --https-proxy, it works fine. Bettercap succeeds in injecting his own self-signed certificate to the web browser. The browser shows the "Not Secure" warning, and lets me accept the invalid certificate by proceeding to the website in an unsecure way.

When I try this command: bettercap -T AddressIpoftheTarget -X --https-proxy it doesn’t work. I don’t understand why the --proxy is needed. Is it because it enables the sslstrip? How does sslstrip contribute in all of this during this scenario?