The MT4 installer from the Metaquotes website will install MT5.
If you want MT4, you must download it from a broker. Not from Metaquotes.
You have to ask Metaquotes why.
It is probably quicker and easier to take the advice and download from a broker...
This has been discussed countless times before.
If you need more information, please use the search function and read the old threads.
There is no point discussing it all again in this thread.