even before the 1mb that satoshi put in during 2010. satoshi had a 32mb limit. this was called the "message size limit"
the reason for 32mb was due to technical stuff outside of blockchain stuff. and more about the internet technical issues

ill leave you to google the technicals but in short its easier to send data in clumps of under 32mb due to increased risk of packet/data loss which can cause propogation delays because so many packets would need to be checked and re sent the bigger the file gets

again this was not a bitcoin/blockchain limitation. it was a internet data transmission procaution to reduce delay, double transmission and other issues.
this is why you see so many image upload services, microsoft word upload, email attachments that have 32mb limits (if they want superfast service withleast chances of data retransmission)

but as i said ill leave you to google the technicals
bigger files are possible but then it requires extra code to double check stuff and need more code to rebuild lost packets etc. so it was simpler to just avoid going that high, to kep the system efficient.