Moq why do mocked methods return null and tests till pass?

I am trying to mock the two interfaces below.

Mock<IEmailSender> emailSender = new Mock<IEmailSender>();
Mock<IEmailTemplate> emailTemplate = new Mock<IEmailTemplate>();

Here is the setup

emailTemplate.Setup(x => x.GetForgotPasswordTemplate(It.IsAny<EmailTemplateViewModel>())).Returns(It.IsAny<string>());
emailSender.Setup(x => x.SendEmailAsync(It.IsAny<SendEmailViewModel>(), default)).ReturnsAsync(It.IsAny<SendEmailResultViewModel>());

Here is the controller action that is called.

[EnableCors(PolicyName = "AllowClientAccess")]
[HttpGet("Forgot")]
    public async Task<IActionResult> ForgotPassword([FromQuery] string email)
    {
        var user = await _userManager.FindByEmailAsync(email);
        if (user != null)
        {
            //MOQ file path not found
            EmailTemplateViewModel model = new EmailTemplateViewModel();
            model.Email = email;
            model.RecipientName = user.UserName;

            var message = _emailTemplate.GetForgotPasswordTemplate(model);

            SendEmailViewModel sendEmailViewModel = new SendEmailViewModel();

            sendEmailViewModel.RecipientName = user.UserName;
            sendEmailViewModel.RecipientEmail = user.Email;
            sendEmailViewModel.Subject = "ForgotPassword";
            sendEmailViewModel.Body = message;

            await _emailSender.SendEmailAsync(sendEmailViewModel);


            return Ok(AddSuccess("Check your email", "Forgot Password"));

        }

        ModelState.AddModelError("Forgot Password","Unable to send email");
        return BadRequest(ModelErrors());
    }

This line returns null

var message = _emailTemplate.GetForgotPasswordTemplate(model);

Here is the method code

 public  string GetForgotPasswordTemplate(EmailTemplateViewModel model)
    {
        try
        {
            var utcNow = DateTime.Now;
            if (_testEmailTemplate == null)
                if (File.Exists("Helpers/Templates/ForgotPasswordEmail.template"))
                    _testEmailTemplate = ReadPhysicalFile("Helpers/Templates/ForgotPasswordEmail.template");


            var appUrl = _configuration.GetSection("ApplicationUrl").Value +
                         "/reset-password?&email=" + model.Email;
            var emailMessage = _testEmailTemplate
                .Replace("{user}", model.RecipientName)
                .Replace("{testDate}", utcNow.ToString(CultureInfo.InvariantCulture))
                .Replace("{appUrl}", appUrl);

            return emailMessage;
        }
        catch (Exception e)
        {
            Log.Warning(e, "Email error");
            throw;
        }
    }

This line also returns null

   await _emailSender.SendEmailAsync(sendEmailViewModel);

Here is the method code

  public Task<SendEmailResultViewModel> SendEmailAsync(SendEmailViewModel model, SmtpConfig config = default)
    {
       
        model.IsHtml = true;
        
        var from = new MailboxAddress(_config.FromName, _config.FromEmail);
        var to = new MailboxAddress(model.RecipientName, model.RecipientEmail);

        return SendEmailAsync(@from, new[] {to}, model.Body, model.Body, config, model.IsHtml);
    }

However the test passes and what i am wondering is why do both of these methods return null and why does the test pass even though it returns null. How do i get these to return something?