4k Playback solution?

Hey, can someone explain in simple terms why my SD625 can playback 4k without any fuss while my core i5(ivy bridge) laptop really struggles and you have to enable High performance for an even decent playback. Also is an android tv a good way yo to playback 4k content.( I am looking into buying a 4k monitor hence the question. Apparently ex uk 27" 4k monitors are available at 20k)

The SD625 officially supports 4K recording and playback (x264 and x265) - https://www.qualcomm.com/products/snapdragon/processors/625

Most streaming platforms use x265 for their 4K content. The standard was established a year or so after the release of Ivy Bridge processors.

CPUs play a major role when it comes to encoding and decoding 4K content.

Thank you, it all makes sense now.