Why that IMG_8558.heic suddenly became 2.8 MB bigger after using iLoveIMG

https://marcogkhc197.huicopper.com/that-moment-with-img-8558-heic-how-to-preview-and-convert-heic-files-before-you-download

Why some web converters, like iLoveIMG, yield much larger JPEGs You uploaded IMG_8558.heic and expected a tidy JPEG. Instead you got a file that is 2.8 megabytes larger than outputs from other tools