As, according to stats and history, Many Dormant BTC addresses (the ones which are not active for a long period of time) is a live proof of Lost Wallets, which means people have lost their wallets/keys to their wallets and now they can't access them. Following are some Dormant Addresses that aren't active (maybe some have become active).
Not all of dormant BTC addresses and Inactive UTXOs are storing lost bitcoin. They can belong to someone who just are in jails but they will be free someday, or someone who have yet wanted to move their coins like diamond-handed Bitcoiners. Dormant addresses are dormant but not actually lost ones.
Most of the analysist says, 20% of the supply of BTC in circulation is wasted because of lost of keys and they have become dormant BTC addresses. But this is just estimation, because no solid stats are provided so, DYOR too.
It is an estimate and with assumption that those inactive UTXOs are all for lost bitcoins. Some very old UTXOs woke up and created panic on the market. We don't know how many inactive UTXOs can wake up after many years.
If you have interest in dormant UTXOs, find something from
https://www.lookintobitcoin.com/charts/hodl-waves/