Why again simply empty app.Run() does we need?

I'm practicing on a simple web api by C# in which I try to see how pipeline goes on. But if I don't add simply empty app.Run() at the end of file, the program terminates immediately, that is, return 0 without running browser. If I write, it works and prints as expected. Must it be at the end of file even if there is app.Run(blablabla)? As far as I know, app.Run() is the terminator delegate.

Simple Program.cs

var builder = WebApplication.CreateBuilder(args);

// Add services to the container.

builder.Services.AddControllers();
// Learn more about configuring Swagger/OpenAPI at https://aka.ms/aspnetcore/swashbuckle
builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();

var app = builder.Build();

// Configure the HTTP request pipeline.
if (app.Environment.IsDevelopment())
{
  app.UseSwagger();
  app.UseSwaggerUI();
}

app.UseHttpsRedirection();

app.UseAuthorization();

app.MapControllers();



app.Use(async (context, next) =>    
{    
  await context.Response.WriteAsync("Before Invoke from 1st app.Use()\n");    
  await next();    
  await context.Response.WriteAsync("After Invoke from 1st app.Use()\n");    
});    
    
app.Use(async (context, next) =>    
{    
  await context.Response.WriteAsync("Before Invoke from 2nd app.Use()\n");    
  await next();    
  await context.Response.WriteAsync("After Invoke from 2nd app.Use()\n");    
});    
    
app.Run(async (context) =>    
{    
  await context.Response.WriteAsync("Hello from 1st app.Run()\n");    
});    
    
// the following will never be executed    
app.Run(async (context) =>    
{    
  await context.Response.WriteAsync("Hello from 2nd app.Run()\n");    
});    


// app.Run(); if we comment in, it works. This style doesn't work.