Looking at the charts here: https://jochen-hoenicke.de/queue/#1,24h I'd say the reason for the delay was the large spike in unconfirmed transactions. That generally drives up fees... and the fee cryptopia added was quite low.
As for the "mysterious" 35BTC... You were withdrawing from an exchange. They obviously had a very large BTC UTXO sitting in their "hotwallet" to cover withdrawals... so they have used that 35BTC "Unspent Transaction Output" (aka UTXO) to pay out your withdrawal.
This transaction generates your UTXO (worth 0.03775726 BTC)... and then Cryptopia gets the 34.95464933 BTC worth of "change". You can read more about change here: https://en.bitcoin.it/wiki/Change
I'd also recommend you read this to understand how Bitcoin works and why UTXOs must be completely spent: https://en.bitcoin.it/wiki/Coin_analogy
Those links are helpful. I learned a whole lot more.
I think this is a going on problem for bitcoin. My other withdrawals from other wallets take way longer too.