A couple of ideas to optimize a file size of this project for your consideration:
1. Convert PNG images with transparency to a WEBP format with a lossy compression. It will reduce a file size on 80% (in 8x times).
You can use a free online image editor: Photopea.com
2. Convert video footage files (snowflakes) in PTE. Use a Convert/Trim Video command and "High Quality" preset. It will reduce a file size on 90% (in 10 times). Video encoder in PTE is very smart and helps to reduce a file size where high bit rate is not necessary.
Without a music this template can be transformed to a slide style about 5 MB.