Wikipedia explains the rationale behind the 1 MB block size limit as follows:
The one megabyte block size limit was added in 2010 by Satoshi Nakamoto as a temporary anti-DoS measure
A SE post expounds on this:
Usually Denial Of Service(DoS) attack may take place on larger sized blocks. So to avoid this condition initially block size Bitcoin was chosen to be 1Mb. Because attacker sends a lot of data in the network to make it busy so that the actual transactions are not able to take place
What I don't understand is:
1) What stops an attacker from sending illegitimate transactions to quickly filling up the 1 Mb block size in order to perform a DoS attack? What is it about bigger block size that makes this attack more likely?
2) Is there a way to empirically demonstrate that a block size of 1 Mb is less likely to suffer a DoS attack compared to a block size of say 1 GB?
Considering the block size is one of the biggest bottle necks to BTC scalability it seems like a no-brainer that something like has to be proven. A block size of 1 GB would be able to process 1,000 x more transactions per sec compared to a block size of 1 mb.