Edit : Holy Shit, i Didn’t Realized this post upvoted so quickly in just a single day, 90+ upvotes, New Record For me I guess…
The full footage shows that the tanks were leaving the square, not entering. They stand in front of them, the driver tries to get around him, they climb on top and chat with the driver for a bit, then bystanders come and walk them away. They have never been identified, their motives never ascertained. It was a divisive time, they could have been stopping them for liberal anti-CPC reasons, they could have been a loyalist counter-protestor insisting they go back to remain in the square, they could have had undiagnosed mental illness and be having a breakdown at really inopportune time, etc