Why you ended up with a WebP
Most websites now serve their pictures as WebP because it is smaller than JPG at the same look. Save a picture from Google Images, a shop or a WhatsApp sticker, and it lands on your device as .webp, which older Windows photo viewers, some editing apps and many upload forms refuse.
Converting to JPG makes the picture open everywhere. The JPG is a little larger than the WebP was; that is normal, and at High quality it looks the same.
Transparency and animation
A WebP can have a transparent background, which JPG cannot keep: see-through parts are filled with white, or the colour you choose. Choose PNG instead to keep them see-through, or use WebP to PNG.
An animated WebP is saved as a single still picture.