"were mainly developed" is a correct phrase and is used in written English.
It is generally used to describe something that has been created or improved over a period of time. Example: These medical technologies were mainly developed over the last decade.
PMCA and Quic were mainly developed for diagnostic purposes, our system with the well defined components was developed to describe quantitatively the prion propagation mechanism using hamster PrP.
Originally, immunocytokines were mainly developed for cancer therapy applications.
The earthflows were mainly developed in flysch-type units, which have already presented high landslide concentrations.
In general, existing risk management techniques or measures were mainly developed for individual financial institutions rather than systems.
Traditionally, signal enhancement techniques for hearing aids (HAs) were mainly developed independently for each ear [1 4].
The mixed siliciclastic carbonate sediments were mainly developed in delta front sandbars and shallow lacustrine underwater uplift beach bars, followed by delta front underwater distributary channels.
Suppose that the signatories to an MEA to reduce emissions of certain gases, say were mainly rich countries and the non-signatories were mainly developing ones.
It was mainly developed by Claude Lévi-Strauss Lévi-Straussh influenced by Durkheim and Mauss as whol as by structural linguistics.
Whereas the first album was mainly developed with early patron Dave Okumu, the new album, Tough Love, features a raft of contributors.
Much of the blame for the unpleasant experiences had by women on dating apps has been put down them being mainly developed in the "boys-club culture" of Silicon Valley.
"The Sphinx is mainly developed for use with remote computing solutions.
