Why in the ISO 8601 calendar, years beginning/ending on Thursdays have 53 weeks? [closed]

That seems weird to me, because common years starting on Thursdays (and leap ones beginning on Wednesdays) have only one month beginning on a Monday: June. why?

Jan 18, 2025 - 10:50
Why in the ISO 8601 calendar, years beginning/ending on Thursdays have 53 weeks? [closed]

That seems weird to me, because common years starting on Thursdays (and leap ones beginning on Wednesdays) have only one month beginning on a Monday: June. why?