Issue while making the bold items of enumerate

I am having an itemize inside and enumerate. I wanted to make the items of enumerate to be bold. But, while using itemize inside the enumerate, I am getting the items of the itemize also bold. I am not able to get the reason why this is happenning!!!

Code:

documentclass[12 pt, a4paper]{book}
usepackage{multicol}
usepackage{geometry}
geometry{a4paper,
          total={170 mm,257 mm}
          left=20 mm,
          top=20 mm,
         }
usepackage{amsmath,bm}
usepackage{amsfonts}
usepackage{amssymb}
usepackage{soul}
usepackage{indentfirst}
usepackage[utf8]{inputenc}
usepackage{palatino}
usepackage[dvipsnames]{xcolor}
usepackage{graphicx}
usepackage{fancyhdr}
usepackage{array}
usepackage{enumitem}
usepackage{mathtools}
usepackage{cancel}
usepackage{arydshln}
usepackage{calc}
usepackage{float}

setlength{parindent}{2em}

newcommand{wt}[2]{underset{substack{textstyleuparrowhidewidthmathstrut#2hidewidth}}{#1}}
definecolor{mygray}{gray}{0.6}

floatstyle{plain}
newfloat{example}{h}{loc}[chapter]
floatname{example}{Example}

begin{document}
 
begin{enumerate}[left=1parindent]bfseries
    item textbf{Enumerate 1 :-}
    begin{itemize}
        renewcommand{labelitemi}{$rightarrow$}
        item Item 1
        item textit{Item 2}
    end{itemize}
end{enumerate}

end{document}

Output:

Can anyone help me with this?

documentclass[12 pt, a4paper]{book}
usepackage{multicol}
usepackage{geometry}
%geometry{a4paper,total={170mm,257mm}left=20mm,top=20mm}
usepackage{amsmath,bm}
usepackage{amsfonts}
usepackage{amssymb}
usepackage{soul}
usepackage{indentfirst}
usepackage[utf8]{inputenc}
usepackage{palatino}
usepackage[dvipsnames]{xcolor}
usepackage{graphicx}
usepackage{fancyhdr}
usepackage{array}
usepackage{enumitem}
usepackage{mathtools}
usepackage{cancel}
usepackage{arydshln}
usepackage{calc}
usepackage{float}

setlength{parindent}{2em}

newcommand{wt}[2]{underset{substack{textstyleuparrowhidewidthmathstrut#2hidewidth}}{#1}}
definecolor{mygray}{gray}{0.6}

floatstyle{plain}
newfloat{example}{h}{loc}[chapter]
floatname{example}{Example}

begin{document}

setlist[enumerate,1]{}%
 
begin{enumerate}[left=1parindent,label=textbf{arabic*.}]
    item textbf{Enumerate 1 :-}
    begin{itemize}
        renewcommand{labelitemi}{$rightarrow$}
        item Item 1
        item textit{Item 2}
    end{itemize}
end{enumerate}

end{document}

documentclass[12 pt, a4paper]{book}
usepackage{multicol}
usepackage{geometry}
geometry{a4paper,
          total={170 mm,257 mm},
          left=20 mm,
          top=20 mm,
         }
usepackage{amsmath,bm}
usepackage{amsfonts}
usepackage{amssymb}
usepackage{soul}
usepackage{indentfirst}
usepackage[utf8]{inputenc}
usepackage{palatino}
usepackage[dvipsnames]{xcolor}
usepackage{graphicx}
usepackage{fancyhdr}
usepackage{array}
usepackage{enumitem}
usepackage{mathtools}
usepackage{cancel}
usepackage{arydshln}
usepackage{calc}
usepackage{float}

setlength{parindent}{2em}

newcommand{wt}[2]{underset{substack{textstyleuparrowhidewidthmathstrut#2hidewidth}}{#1}}
definecolor{mygray}{gray}{0.6}

floatstyle{plain}
newfloat{example}{h}{loc}[chapter]
floatname{example}{Example}

begin{document}
 
begin{enumerate}[left=1parindent,font=bfseries]
    item textbf{Enumerate 1 :-}
    begin{itemize}
        renewcommand{labelitemi}{$rightarrow$}
        item Item 1
        item textit{Item 2}
    end{itemize}
end{enumerate}
end{document}