Yeah this is super common when you switch niches on an established account. The algorithm built a viewer profile based on what was working before, so now it's showing your new content to people who don't actually want it. They scroll past, engagement tanks, the algo decides your new stuff is bad.
Two real options here:
Option A: Push through on the existing account. Post new-niche content consistently for 3-4 weeks, accept the bad reach, and eventually the algo rebuilds your audience profile. You'll lose some of the football card followers but keep the ones who actually like you as a creator. Works if you're patient.
Option B: New account. Clean slate, no confused algorithm, no disappointed old followers. You lose the 8k head start but grow cleaner and faster long term.
Honestly, for most people I'd say option B. The carryover from a niche pivot is usually smaller than people think, and starting fresh means you get to redesign the account around what you actually want to be known for. The 8k on the old account is basically vanity at this point, it isn't translating to anything useful for your Pokémon content.
If you go with option A, don't do hybrid content trying to bridge the two niches. That just confuses the algo worse. Go 100 percent Pokémon and let it sort itself out.