Many mobile apps and desktop editors (like iMovie or Windows Photos) use this naming convention if you don't provide a custom title. For example, Gifu Seiki Industrial uses this file name for technical demonstration clips on their corporate site.
Use a tool like ExifTool to see the "Create Date" and the software used to generate it, which can clarify if it's a legitimate personal file. MyVideo_1mp4
Upload the file or the URL to a service like VirusTotal to check for hidden scripts. Many mobile apps and desktop editors (like iMovie
Universities and research centers often host student presentations or data clips under this name. For instance, Texas A&M University uses similar generic naming for various academic poster video components. MyVideo_1mp4