intuitive interpretation Fourier Transform of two different Rectangular pulses
Note that the peak height of the Fourier transform of a wider rectangular function is proportionally higher.  This is necessary to preserve total energy, as per Parseval's theorem.  However, the energy required to create the sharp edges of a rectangle in the time domain is still out there on the tails of the Sinc function in the frequency domain, roughly the same (but more wiggly).

But when you scale the vertical axis of 2 plots so that they have the same peak height, the envelope of the FT of a wider rect function looks narrower in the plots of that transform.  But that's only in relation to the peak with a scaling applied.