If you ever had a read on the original mailing list conversation between SN and his first repliers you should notice how SN was able to solve pragamtically and theoritically all the limits he encountered when planning theory about Bitcoin itself and which other people pointed out.
That is because at that moment, SN was the centralized, undisputed authority of bitcoin's protocol (something that Core thought, had inherited for good from SN, like the Pope from Jesus himself). Satoshi decided by himself, after hearing about remarks and so on, about bitcoin and its protocol.
I simply cannot believe that he eventually thought that a 1 MB block would be ok to handle a certain amount of transaction in a mass scale view: ok it was 2008/2009 (and maybe even years before while he was working hidden from public announcements) but already at that time the HDD capabilities and internet connections speeds were enough over the 1 MB scale.
There should be something hidden between the lines that community still doesn't know.
Well, obviously, 1 MB blocks were not OPENLY part of his view on bitcoin, nor in his 2008 post, nor in the thread I linked. After people pointing out the fundamental difficulty of changing a protocol rule in a large network (especially a network which has been designed to resist change) he replied that "one simply would have to change the few lines of code".
Now, this can only mean two things.
1) Satoshi, being so used to be able to change the rules all by himself, had difficulties imagining that this would not be possible some years later (like Core attempted) - even though people told him that miners might oppose to a change as it would be lucrative to them. In other words, Satoshi didn't fully grasp the immutability of the protocol himself (that's what I think).
2) Satoshi secretly wanted small blocks for different reasons that he could not admit publicly at that time:
a) because he was an evil genius on the payroll of the Rothschilds
b) because he had realized that his sound money doctrine, and reducing the block reward, would need fees for his mega mining farms to exist, so the miners should be able to squeeze out the users and he had secretly given up on bitcoin becoming money to buy your coffee with, and only gold for rich whales
c) Satoshi had build in a self-destruction bomb in bitcoin if ever the community couldn't come to a positive consensus over it
d) some other reason that could not be admitted back then but that were part of his almighty genius
I go for 1), because there are many OTHER issues with bitcoin, where Satoshi said that one could change the protocol if the need arose, like if ever the elliptic curve signature scheme became compromised, or some other cryptographic aspect turned out not to be secure, like when the hash function for PoW turned out to be cracked or so.
Also, all his solutions for that (namely, nodes automatically submitting transactions of all the existing wallets to new cryptographical protocols) would generate so many transactions (essentially a transaction per UTXO) that 1 MB blocks could never sustain such a protocol change.