To big for the comment ...
An MWE which reproduce your problem can be:
\documentclass{article}
\usepackage{graphicx}
%---------------- Show page layout. Don't use in a real document!
\usepackage{showframe}
\renewcommand\ShowFrameLinethickness{0.15pt}
\renewcommand*\ShowFrameColor{\color{red}}
%---------------------------------------------------------------%
\usepackage{lipsum}% For dummy text. Don't use in a real document
\begin{document}
\lipsum[1-3]
\begin{figure}[hbt] % if here is enough space for image,
% it will follow above text, if not
% it will be moved to top of the next page
\centering
\includegraphics[height=54mm]{example-image-duck} % I haven't your image,
% therefore a example image is used
\caption{Interaksi antara agen dan lingkungan pada \textit{Finite Markov Decision Processes}}
\label{baganMDP}
\end{figure}
\lipsum[4-6]
\end{document}
and in is image at the bottom of page since after point of its inserting into text is enough space for it. For example, if the image is one millimeter higher, it will be moved to the top of the next page.
This MWE you should adopted to your document. Used preamble as well image size is unknow to us so please test above example with your document preamble and image.
If you will have around image large white space, than your image has this space around it. This can you test by inserting image in frame:
\frame{\includegraphics[height=55mm]{example-image-duck}}
If white space between image and frame is bigger then few point (width of \fboxsep), than you need firs trim out this space with dome graphicx tool.
A case, when on page is enough space for figure:

A case, when on page is not enough space for figure (it is one milimeter higher as before:

(red lines indicate page layout)
[h]so have prevented the figure being placed at the top (t) or bottom (b) of a page you also omittedpwhich prevents it being placed on a foat page but it was eventually forced on to a float page as an emergency recovery. try[htbp]to allow more options. – David Carlisle Dec 15 '21 at 16:19[ht]then it will go at teh top of the current or next page unless you ahve something you have not shown that stops that – David Carlisle Dec 15 '21 at 16:24\rule{2cm}{3cm}instead of\includegraphicsand useone two three... one two three...as the words, just arrange that a page has the same general for as your real cas, and the image does not appear where you expect. – David Carlisle Dec 15 '21 at 16:26