After some tryes I found the problem.
No the fault is not about port 80, browser or any other faboulus things between esp32 and the user.
server.serveStatic("/assets/", SPIFFS, "/assets/").setCacheControl("max-age=31536000");
I used this function for serve pages with cahce, not exactly, the function whas this:
server.serveStatic("/", SPIFFS, "/").setCacheControl("max-age=31536000");
I don't know exactly why, but what was after this was drasticaly slow.
After moving all my "api" endpoint before, response are faster then the other server in the other ports.
Furthermore using:
server.serveStatic("/", SPIFFS, "/").setCacheControl("max-age=31536000");
don't set automatically the cache header of the web pages stored in the "/" folder, cause there's a server.on listenging for that url, the cache header is applyed only if you are going to get the file.
Ex:
http:/espipaddres/page.html -> will have cache header
http:/espipaddres/page
with a
server.on("/page", HTTP_GET, [](AsyncWebServerRequest * request) {
request->send(SPIFFS, "/page.html", "text/html");
});
will not have cache header