Internet Faster After Releasing IP???

I have Spectrum 1Gbps internet. For the last few weeks my internet has been much slower than usual. Typically I get in the 900mbps range on wired, but lately, it has been high 200- low 300 range. Websites have been taking forever to load across the board. Weirdly enough, I would get in the 600mbps range when connected to VPN. I started to wonder if maybe Spectrum was specifically throttling my IP address, so I forced my modem to release it and obtain a new one. Now I'm getting back in the 900mbps range without the VPN. So was my throttling theory correct or are there other explanations for what was going on?