The answer can be split in both ‘Yes’ and ‘No’ part.
The Undertaker, now 52 years old, has been one of the biggest draws for WWE for nearly 3 decades. He has sold arenas after arenas, and has fans in legion. In fact, he is possibly the biggest WWE superstar ever. (Yes, even better than Steve Austin, HBK and Ric Flair.)
However, Undertaker had been struggling with loads of health issues even before WM 30 in 2015. He had only been making Wrestlemania appearances. His matches against Shawn Michaels, Triple H and CM Punk took him to the tipping points. In fact, his match against Triple H at WM 27 ended with him getting carried backstage on a carriage vehicle. This, in itself, displayed the kind of health Undertaker had been struggling with—and even then he’d have physically tormenting WM matches. (Talk about legend!)
WWE writers and management were very well aware of this fact. And they knew the end for Taker’s wrestling career was sooner than later. So assumingly, they decided to make the most of him till he is here. And what better way doing that than breaking his 21 years’ old Wrestlemania streak and giving rise to the biggest heel in this industry!
Not that Brock Lesnar wasn’t already an established heel at that time. However, after defeating Undertake at WM 30, he came out as the biggest heel for WWE and a complete badass to do something that so many superstars couldn’t accomplish in 21 years, i.e. break Taker’s undefeated streak. After that, the stature of Lesnar grew to another level. And he became the biggest draw for WWE (and UFC as well – remember he made a comeback to octagon and defeated Mark Hunt?).
Brock Lesnar is still wrestling industry’s hottest name right now. And a major credit for that goes to the decision of him defeating Taker at WM.
So yes, WWE was right in deciding to end Taker’s streak. This made Lesnar the topmost star. And ended up making WWE more money than ever!
On the other hand, the decision to end a streak that took 21 years to built, it sounds like a very bad idea. The streak was Taker’s biggest legacy. And when WWE decided to end it, they – in many ways – shook this legacy. This, however, doesn’t mean Undertaker became any less great. In fact, after his defeat against Lesnar, he received more respect than ever for letting his decades’ long hard work go by just to help the company more money.
So yes, on WWE part, ending Undertaker’s Wrestlemania streak was both a good and bad idea.All being said, with or without streak, Undertaker – real name Mark Calaway – was, still is, and always will be the greatest name in wrestling history.