Modifying list issue, C#

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//Rextester.Program.Main is the entry point for your code. Don't change it.
//Compiler version 4.0.30319.17929 for Microsoft (R) .NET Framework 4.5

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;

namespace Rextester
{
    public class Program
    {
        public class Vehicle
        {
            public int number { get; set; }
            public List<Properties> property { get; set; }
        }
        
        public class Properties
        {
            public int maxSpeed { get; set; }
           
            public bool isTwoDoor { get; set; }
        }
        
        public static void Main(string[] args)
        {
            List<Vehicle> mainList = new List<Vehicle>();
            List<Properties> defaultPropertyList = new List<Properties>{
                new Properties() { maxSpeed = 0, isTwoDoor = true },
                new Properties() { maxSpeed = 0, isTwoDoor = true },
            };
            
            
            mainList.Add(
                new Vehicle() {
                    number = 1,
                    property = new List<Properties>(defaultPropertyList)
                }
            );
            mainList.Add(
                new Vehicle() {
                    number = 2,
                    property = new List<Properties>(defaultPropertyList)
                }
            );

foreach(Vehicle vehicle in mainList) {
                Random rnd = new Random();
                vehicle.property.ForEach(x => x.maxSpeed =  rnd.Next(1, 100));
            }
            
            foreach(Vehicle vehicle in mainList) {
                foreach(Properties property in vehicle.property) {
                    Console.WriteLine("Vehicle: " + vehicle.number + ", maxSpeed: " + property.maxSpeed);
                }
            }
        }
    }
}

Show compiler warnings [ + ] Show input
Compilation time: 0,14 sec, absolute running time: 0,08 sec, cpu time: 0,08 sec, average memory usage: 13 Mb, average nr of threads: 3