What exactly is "The plugins {} block must not be used here. If you need to apply a plugin imperatively"? - gradle

Question

I have a gradle project that uses kotlin dsl:
plugins {
base
kotlin("jvm") version "1.3.70" apply false
}
//val scalaV: String by project
//val ext = SpikeExt(this)
allprojects {
apply(plugin = "java")
apply(plugin = "scala")
group = "com.tribbloids.scalaspike"
version = "1.0.0-SNAPSHOT"
repositories {
mavenCentral()
jcenter()
maven("https://dl.bintray.com/kotlin/kotlin-dev")
}
dependencies {
}
}
when I run gradlew build I encounter the following error:
FAILURE: Build failed with an exception.
* Where:
Script '/home/peng/git/scalaspike/build.gradle.kts' line: 1
* What went wrong:
The plugins {} block must not be used here. If you need to apply a plugin imperatively, please use apply<PluginType>() or apply(plugin = "id") instead.
* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.
* Get more help at https://help.gradle.org
BUILD FAILED in 870ms
In the mean time, the exact identical line 1 works normal in the other project:
https://github.com/gradle/kotlin-dsl-samples/tree/master/samples/multi-kotlin-project
plugins {
base
kotlin("jvm") version "1.3.70" apply false
}
allprojects {
group = "org.gradle.kotlin.dsl.samples.multiproject"
version = "1.0"
repositories {
jcenter()
}
}
dependencies {
// Make the root project archives configuration depend on every sub-project
subprojects.forEach {
archives(it)
}
}
So I have 2 questions:
what does this mean?
why the same thing works in the second project but fails on the first project? What is the difference?