1 MB Block Size as a Anti-DoS Attack Measure 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.
Thanks
The DoS the block size limitation is trying to prevent is a miner creating a huge block of garbage data that now every single Bitcoin miner must download, validate, and store the entirety of. Imagine if some miner decided to create block after block of 1GB of garbage, and now every single Bitcoin node in the world must store and validate all of this garbage. If it were possible, this would be in the best interests of larger miners to do: smaller miners, who don't have the ability to download and validate these giant blocks of garbage as efficiently, will not be able to keep up with mining.
Also, people do attempt to submit spam to the blockchain. Trying to do so to the point of blocking out legitimate transactions will be quite expensive, considering you would have to pay transaction fees for every &quot;spam&quot; transaction you want to send.