Bitcoin is a technology that offers something that did not existed before and offers freedom in a world where that freedom is under threat every single day and as such bitcoin is a valuable asset, can bitcoin develop bubbles? Yes, is bitcoin a bubble? No, because unlike tulips bitcoin is useful and its value derives from that usefulness and the more people adopt it the more useful it becomes increasing its value accordingly.
Yeah, bitcoin must be an all-new system which hasn't been experienced by human never before hence its growth as well at never seen pace and level. People who understand these never call bitcoin's value appreciations as bubble. But for the people who just see bitcoin like another stock or asset might lead to assume like it is growing for no reason and may get burst at any time; but when they start learning about bitcoins then they will definitely change their view.
I read somewhere that 2017's rise was up to the level of bubble like the actual growth for bitcoin in 2017 should be like up to 10k and anything beyond that in 2017 was bubble. Still, I am not ready to accept that because, in some calculation grows 100x from previous cycle's low and that way 19k in 2017 was not a bubble and still deserved growth by 2nd halving.