how to avoid keyword Cannibalization

I created following pages

domain.com/coupon/lazada
domain.com/coupon/shopee
etc

I link coupon page domain.com/coupon to the rest with exact keywords like "lazada coupon" "shopee coupon". Subpages also link back to the coupon page with anchor text like "coupon" "promo code" "discount".

on some pages, instead of rank for Subpage google rank the coupon page in page 5. How to avoid that?

I also create support pages like

domain.com/coupon/lazada/voucher
domain.com/coupon/lazada/promo-code

To support Lazada page for keyword Lazada promo code, lazada voucher, etc and do the same. Have the same problem, Google even selects support page to rank for the main keyword "Lazada coupon"