Hello ! I have a problem with this slide with animation the layout of the figure and the text changes

Question

\documentclass[xcolor=table]{beamer}

\usepackage[american,francais]{babel}
\usepackage{listings}
\usepackage{microtype}
\usepackage{textcomp}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{lmodern}
\usepackage[final]{pdfpages}
\usepackage{smartdiagram}
\usepackage{tikz}
\usetikzlibrary{arrows.meta}
\usetikzlibrary{shadows.blur}
\usetikzlibrary{shapes.symbols}
\usetikzlibrary{shapes,arrows}
\usetikzlibrary{positioning}
\usepackage{relsize}
\usepackage{mathtools,amsmath}
\usepackage{graphics,bm}
\usepackage{pifont}
\usepackage{color}
\usepackage{calligra}
\usepackage{verbatim}
\usepackage{amsfonts,amsmath,amssymb}
\usepackage[T1]{fontenc}
\usepackage{graphicx}
\usepackage{forest}
\usetikzlibrary{arrows.meta, shapes.geometric, calc, shadows}

\colorlet{mygreen}{green!75!black}
\colorlet{col1in}{red!30}
\colorlet{col1out}{red!40}
\colorlet{col2in}{mygreen!40}
\colorlet{col2out}{mygreen!50}
\colorlet{col3in}{blue!30}
\colorlet{col3out}{blue!40}
\colorlet{col4in}{mygreen!20}
\colorlet{col4out}{mygreen!30}
\colorlet{col5in}{blue!10}
\colorlet{col5out}{blue!20}
\colorlet{col6in}{blue!20}
\colorlet{col6out}{blue!30}
\colorlet{col7out}{orange}
\colorlet{col7in}{orange!50}
\colorlet{col8out}{orange!40}
\colorlet{col8in}{orange!20}
\colorlet{linecol}{blue!60}
\newcommand{\crossed}{\item[\ding{229}]}
\newcommand{\crossedb}{\color{blue}\item[\ding{229}]}
\newcommand{\crossedc}{\color{laughlingray}\item[\ding{229}]}
\newcommand{\cro}{\item[\ding{72}]}
\newcommand{\crob}{\item[\color{laughlingray}\ding{72}]}
\newcommand{\elyes}{\item[\ding{77}]}
\newcommand{\ahmed}{\item[\ding{78}]}
\newcommand {\bigsize}{\fontsize{7.75pt}{20pt}\selectfont}
\usetheme[language=french]{Laughlin}
\newcommand{\acronym}[1]{\textsc{\lowercase{#1}}}
\newcommand{\command}{\texttt}
\newcommand{\email}[1]{\href{mailto:#1}{\texttt{#1}}}
\newcommand{\familyname}{\textsc}
\newcommand{\filepath}{\texttt}
\newcommand{\latexcode}{\texttt}
\newcommand{\parameter}[1]{\textlangle #1\textrangle}

\lstset{basicstyle=\ttfamily,keywordstyle=\color{laughlinblue}\bfseries,commentstyle=\color{laughlinblue!75}\itshape,columns=flexible}

\begin{document}
\begin{frame}
\frametitle{\small Cahier des charges\normalsize}

\vspace{-0.25cm}
\small
\begin{itemize}
\cro<1->Trajectoire de référence
\cro<2->Angle de lacet de référence $\psi_d$
\cro<3->L’angle de roulis $\phi_d$ et l’angle\\ de tangage $\theta_d$ seront nulles
\end{itemize}\normalsize

\vspace{-3cm}
\begin{figure}
   \includegraphics<1->[height=.3\textwidth]{Figures/chap3/trajetref.jpg}\hspace*{-5.5cm}
   \vfill
   \includegraphics<2->[height=.3\textwidth]{Figures/chap3/psiref.jpg}\hspace*{-5.5cm}
\end{figure}
\end{frame}
\end{document}

Answer 1

• sorry, your question is not clear, so the mwe below is based on guessing
• frankly said, preamble of your document is one big mess: some packages are loaded twice, the same is valid for tikz libraries etc
• you should carefully read both answers to your previous question: How to reduce the size of this forest?. there in my answer i clear the same preamble ...
• please test mwe below in see, if it provide what you looking for (in real document you should delete demo option in \documentclass...

• in mwe are changes in comparison to your code of the frame's content indicated by % <---

  \documentclass[xcolor=table, demo]{beamer}
  
  \usepackage[american,francais]{babel}
  \usepackage{textcomp}
  \usepackage{pifont}
  \usepackage{microtype}
  
  \newcommand{\cro}{\item[\ding{72}]}
  
  \begin{document}
  \begin{frame}
  \frametitle{Cahier des charges} % <---
  \small
  \begin{itemize}[<+->]     % <---
  \cro    Trajectoire de référence
  \cro    Angle de lacet de référence $\psi_d$
  \cro    L’angle de roulis $\phi_d$ et l’angle\\ de tangage $\theta_d$ seront nulles
  \end{itemize}
  %
      \begin{figure}
  \onslide<1->{\includegraphics[height=.25\textwidth]{Figures/chap3/trajetref.jpg}} % <---
     \vfill
  \onslide<2->{\includegraphics[height=.25\textwidth]{Figures/chap3/psiref.jpg}} % <---
      \end{figure}
  \end{frame}
  \end{document}