I’m actually using LiipImagineBundle to optimise sizes of my images, and I tried to convert my images to wepb, but images generated are now heavier than before

There is my liip_imagine.yaml :

liip_imagine:
  # valid drivers options include "gd" or "gmagick" or "imagick"
  webp:
    generate: true
  driver: "gd"
  resolvers:
    default:
      web_path: ~
  twig:
    mode: lazy
  loaders:
    default:
      filesystem:
        data_root: '%kernel.project_dir%/var'
  # This is where all the filters sets are located
  filter_sets:
    large_image:
      format: 'webp'
      quality: 75
      filters:
        thumbnail:
          size: [ 960, 550 ]
          mode: 'outbound'
    medium_image:
      format: 'webp'
      quality: 75
      filters:
        thumbnail:
          size: [ 630, 350 ]
          mode: 'outbound'
    small_image:
      format: 'webp'
      quality: 75
      filters:
        thumbnail:
          size: [ 330, 200 ]
          mode: 'outbound'

there is my twig :

 <picture>
     <img type="image/webp" srcset="{{ asset('/gallery/'~ myimage)|imagine_filter('small_image') }} 480w,
     {{ asset('/gallery/' ~ myimage)|imagine_filter('medium_image') }} 768w,
     {{ asset('/gallery/' ~ myimage)|imagine_filter('large_image') }} 1024w"
     sizes="100vw" loading="lazy">
</picture>

It generate me and url like : https://image.com/media/cache/small_image/gallery/myimage.jpg.webp

but I go from a 70kb image to a 240kb image

Some one have an idea to how can I solve this issue ?
Thank