Jesus did not return in 70 AD. That is a cultic belief. Jesus himself warned against anyone telling us he came "secretly."
On your other issue: why did God allow the sacrifice of animals before Jesus?
This is a curious statement for a dispensationalist, since a central tenet of dispensationalism is the "secret rapture" of Jesus when He "descends from heaven" for His church seven years before His visible second coming. And then we are supposed to believe there will be 144,000 Jewish evangelists running around telling about this "secret coming" and how to prepare for the real second coming. There is a disconnect which I'm sure you have rationalized in your system.
Maybe it's just semi-secret. Will unbelievers be able to see Jesus when He comes secretly for His church? Will unbelievers be able to witness bodies shooting up out of the ground and vanishing into thin air, but not actually see Jesus in bodily form? Perhaps you can exegete a passage or two to explain all this to us.
For the record, I'm not endorsing any "secret" second comings of Jesus.