In order to achive this, you need to add the below code in your styles.css file
.wp-video, video.wp-video-shortcode, .mejs-container, .mejs-overlay.load {
width: 100% !important;
height: 100% !important;
}
.mejs-container {
padding-top: 56.25%;
}
.wp-video, video.wp-video-shortcode {
max-width: 100% !important;
}
video.wp-video-shortcode {
position: relative;
}
.mejs-mediaelement {
position: absolute;
top: 0;
right: 0;
bottom: 0;
left: 0;
}
.mejs-controls {
display: none !important;
visibility: hidden !important;
}
.mejs-overlay-play {
top: 0;
right: 0;
bottom: 0;
left: 0;
width: auto !important;
height: auto !important;
}