The purpose of this default limitation is for whom has too many events in his calendar from old history.
Usually, user can select the events by filter and sort feature.

However in your case, you want total 4 views for 4 months, so it needs to get over 100 events.
You can set maxItems to bigger number (e.g: 500)
https://github.com/eouia/MMM-CalendarExt2/wiki/2c.-Configuration:View#common

{
  module: 'MMM-CalendarExt2',
  config: {
    updateInterval: 1000 * 60,
    calendars: [
      ...
    ],
    defaultSet: {
      view: {
        hideOverflow:false,
        timeFormat: "h:mm A",
        maxItems: 500,  // < ------ THIS VALUE
      }
    },
    views: [
      {
          mode: "month",
          name: "Monthly Calendar",
          position: "middle_center",
      },
      ...
    ],
    scenes: [
      {
        name: "current",
        views: ["Monthly Calendar"],
      },
      ...
    ],
  }
},

You can get this.

    		],
    		views: [
				{
						mode: "month",
						name: "Monthly Calendar",
						position: "middle_center",
						hideOverflow: false,
						timeFormat: "h:mm A",
				},
				{
						mode: "month",
						name: "Next Month",
						position: "middle_center",
						hideOverflow: false,
						timeFormat: "h:mm A",
						fromNow: 1,
				},
				{
						mode: "month",
						name: "Next Next Month",
						position: "middle_center",
						hideOverflow: false,
						timeFormat: "h:mm A",
						fromNow: 2,
				},
				{
						mode: "month",
						name: "Last Month",
						position: "middle_center",
						hideOverflow: false,
						timeFormat: "h:mm A",
						fromNow: -1,
				},
    		],
    		scenes: [
				{
					name: "current",
					views: ["Monthly Calendar"],
				},
				{
					name: "next",
					views: ["Next Month"],
				},
				{
					name: "next_next",
					views: ["Next Next Month"],
				},
				{
					name: "before",
					views: ["Last Month"],
				},

    		],
    	}
	},