I found out why. I enabled the TLS 1.3 protocol on NGINX. Chrome 70 on Win10 handshaked to TLS 1.3 without http/2. As soon as I disabled TLS 1.3 the browser handshaked to TLS1.2 + https/2. The question, of course, is what is faster. I opted for the TLS1.2 + https/2 scenario.
I found out why. I enabled the TLS 1.3 protocol on NGINX. Chrome 70 on Win10 handshaked to TLS 1.3 without http/2. As soon as I disabled TLS 1.3 the browser handshaked to TLS1.2 + https/2. The question, of course, is what is faster. I opted for the TLS1.2 + https/2 scenario.