Cannot set (let) mapleader and use <leader> in global vimrc

Question

I'm using basic version vimrc from https://github.com/amix/vimrc. No problem if I put the vimrc file to /home/{user}/.vimrc, but if I put it in /etc/vimrc (arch) or /etc/vim/vimrc (debian), it became problems.

The problem is: I cannot use:

let mapleader = ","

And then use the mapping function that use the leader:

map <leader>tf :tabnew **/*    "fuzzy search file and open in new tab
map <leader>tn :tabnew<cr>     "open a blank new tab

Or just mapping a <space>:

map <space> /
map <c-space> ?

In my arch workstation, I open it from konsole. In my debian server, I ssh-ed to it (so, a tty).

Any suggestion? Thanks.

Edit (more information) with command :map with global vimrc (from @statox link):

   0             ^
   <Leader>m   * mmHmt:%s/<C-V><cr>//ge<cr>'tzt'm
v  <C-S-k>       :m'<-2<cr>`>my`<mzgv`yo`z
v  <C-S-j>       :m'>+<cr>`<my`>mzgv`yo`z
n  <C-S-k>       mz:m-2<cr>`z
n  <C-S-j>       mz:m+<cr>`z
   <leader>cd    :cd %:p:h<cr>:pwd<cr>
   <leader>te    :tabedit <c-r>=expand("%:p:h")<cr>/
   <leader>tf    :call fzf#run({'sink': 'tabedit'})<cr>
   <leader>tc    :tabclose<cr>
   <leader>tn    :tabnew<cr>
   <leader>tz    :tabnew **/*
n  <c-space>   * ?
n  <space>     * /

So, most of the keys are not mapped correctly except a few like map 0 ^

And this is :map command when I drop the vimrc to ~/.vim/vimrc

   0             ^
   ,m   * mmHmt:%s/<C-V><cr>//ge<cr>'tzt'm
v  <C-S-k>       :m'<-2<cr>`>my`<mzgv`yo`z
v  <C-S-j>       :m'>+<cr>`<my`>mzgv`yo`z
n  <C-S-k>       mz:m-2<cr>`z
n  <C-S-j>       mz:m+<cr>`z
   ,cd    :cd %:p:h<cr>:pwd<cr>
   ,te    :tabedit <c-r>=expand("%:p:h")<cr>/
   ,tf    :call fzf#run({'sink': 'tabedit'})<cr>
   ,tc    :tabclose<cr>
   ,tn    :tabnew<cr>
   ,tz    :tabnew **/*
n  <c-space>   * ?

Answer 1

I'll list my alternative ideas that doesn't solve the actual problem:

1. put the vimrc file elsewhere (prefer in /etc/skel/.vim/vimrc) then make a softlink to local .vim/vimrc. The command: mkdir .vim && sudo ln -s /etc/skel/.vim/vimrc .vim/vimrc