why form in front-page.php redirect to blog page

Because, by default, if you don’t specify an actual page in the target, it assumes you meant www.example.com/ , which goes to the www.example.com/index.php page, which loads the home page of your site, which is the front page of your site, which is normally the blog page (unless you specify a static page as the ‘home’ page of your blog). (Simple explanation…)

So, you need to go to the page that processes the form. If it is itself, then you need to use this in the ‘action’ parameter:

action="<?php get_permalink();?>"

Which will return the link of the current page, which I assume has the processing code for your form.

Correction

You need to use the_permalink(), not get_permalink(). For the reason why, see here.