iPhone, for non-iMessage recipients, was limited by MMS limits.
Who sets the MMS limits? the telcos - actually min(both ends), the iPhone sender's telco and the recipient's telco.
iMessage was introduced in 2011. see https://en.wikipedia.org/wiki/IMessage
Google announced RCS support for Google Messages in 2019. from https://en.wikipedia.org/wiki/Rich_Communication_Services
"In June 2019, Google announced that it would begin to deploy RCS on an opt-in basis via the Messages app, with service compliant with the Universal Profile and hosted by Google (i.e. Jibe) rather than the user's carrier, if the carrier does not provide RCS."
Before 2019, Android users depended on their telco to support RCS. The RCS wikipedia article talks about Samsung support for RCS in USA in 2015 and Android Lollipop OS users getting RCS support - but they still needed telco support.