Sorry to learn about your lost funds.The biggest mistake here was that you had not enabled 2FA authentication to your mail id, by gaining access to your mail id ,your other accounts may also be on stake. If your mail password is still working just change it immediately and set 2 FA to all your mail ids (including backup mail id). I can understand of having 1 tier security to your account if little funds were kept there but this amount was in 5 figures then 2 tier security should be there.