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

https://atavi.com/share/xno19gz1utnn5

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