Globally, Android has 3/4 of the market share. In India, for example, Android currently dominates the market with 95.1 per cent market share while Apple iOS has 3.93 per cent share.
Hence, scammers target Android users and create malware for Android devices rather than for Apple. It is not that Apple devices are more secured. For scammers, it is business for them, no matter if their business is illegitimate or illegal, but they also obviously will operate their businesses in a way that they target their widest possible audience. Therefore, they do not waste their time coding to target Apple devices, they target Android devices, in order to manage their R&D and coding time more effectively and also to increase their profitability.
But, it is really good that cyber security and antivirus companies are also doing their R&D and releasing regular updates to patch malware.